[HN Gopher] I fixed a parasitic drain on my car in 408 days
___________________________________________________________________
I fixed a parasitic drain on my car in 408 days
Author : dmuller
Score : 227 points
Date : 2023-04-10 15:40 UTC (7 hours ago)
(HTM) web link (davidmuller.github.io)
(TXT) w3m dump (davidmuller.github.io)
| umvi wrote:
| I have a 2013 Mazda 3 and I've had to replace the battery every
| year for the past 3 years. I wonder if I have this exact same
| problem? I don't want to disable the wireless key system though
| because I like being able to lock/unlock the car without pulling
| the keys out of my pocket. Is there an alternative to this
| workaround?
| depingus wrote:
| Thanks for this timely post. I'm literally in the middle of
| running down a parasitic drain on my Nissan Xterra.
|
| I tracked mine down using a different method which helps when
| your fuses don't all have test points (and no conversion table
| needed).
|
| - Disconnect negative battery cable
|
| - Switch your multimeter to 10A (don't forget to swap lead ports)
|
| - Connect the multimeter in-line between the negative cable and
| negative battery post
|
| - The readout on the multimeter should now tell you how much
| drain you have
|
| - Start pulling fuses one by one until you see the amps drop to
| normal
| Scoundreller wrote:
| And pro-tip if you need to go down the line past the fuse box:
| if you have a DC clamp-on ammeter, you can do multiple windings
| to 2x or 3x the current readings for smaller draws that the
| clamp-on might not pick up on.
| justnotworthit wrote:
| Whoa, thank you. I was disappointed to read in my
| multimeter's manual (klein CL800) that the resolution for DC
| (up to 60A, if I'm reading "range" in the chart correctly)
| was only 10mA.
| binkHN wrote:
| Had a similar issue with a 1.5-year-old vehicle that would have
| the battery fully drained in a little over a week if the vehicle
| wasn't driven. Had the dealership "fix" the problem three times
| and the problem was never fixed. I used the lemon law to get a
| brand new vehicle. I won't name the brand, but dealing with the
| manufacturer for this was rather trouble free.
| arscan wrote:
| Wow, I have a 2012 Mazda3 and have the same problem, which only
| really surfaced during the pandemic when I stopped driving my car
| regularly. The dealer said it was just a normal level of drain
| (even though it would die in just 4 days of non-use) and I should
| get a trickle charger. Which I did, and is annoying, but is
| something that I can deal with. I'm not sure if I'm willing to
| disconnect my remote entry to see if this fixes it, but I'm glad
| others have seen similar behavior because it really bugs me that
| the mechanics would just shrug and not really diagnose why this
| was happening.
| vivalibre wrote:
| There is a YouTube channel that has a lot of excellent content on
| finding and fixing parasitic electrical draws. Pine Hollow Auto
| Diagnostics.
|
| nb: I am not affiliated with this chan, just a fan.
| NotYourLawyer wrote:
| I had a car that would drain its battery if you let it go a week
| or two without driving it. I just got a trickle charger and left
| it connected, problem solved.
|
| Not really a great option to leave the hood up all the time if
| you park outside though.
| blobbers wrote:
| Is it possible the key fob just needs replacement and is causing
| the intermittent sleep failure?
| buescher wrote:
| My conjecture: there is ambient RF noise on key fob's frequency
| (most likely 315MHz), which is causing the key fob receiver
| circuit to remain active and process any signals that it
| receives, rather than going to sleep and periodically waking up
| to check for incoming transmissions.
| leviathant wrote:
| That's probably what the author was thinking in February 2022
| when they removed the batteries from their keyfob and only used
| the metal backup key, only to have the problem resurface less
| than a year later. It's probably safe to say that without
| batteries, the fobs were having no effect on the keyless system
| housed within the car.
| instaclay wrote:
| I was also curious about this.
|
| Maybe the keyless entry computer stays awake to try to sync
| with a fob and then sleeps on success? If a user chooses not to
| use a fob at all, maybe it stays awake indefinitely trying to
| find a key to sync with.
| blobbers wrote:
| Yeah sleep-wake problems often are related to things missing
| or broken in the (poorly constructed) system.
|
| If the software on the car was poorly written, it may not
| have had a good back-off on the fob check, or if the fob
| itself was malfunctioning it may have left the car in a weird
| state.
|
| While I wouldn't expect a fob to drain a car, it certainly
| doesn't seem implausible, especially given what the fix is.
| Captaffy wrote:
| [dead]
| fullstop wrote:
| Thinking this through a little bit further, I am wondering if
| subsystems can wake up if someone else uses their fob but the
| key signal doesn't match. Surely, at some level, something has
| to wake up to validate this.
| sixstringtheory wrote:
| Back when I was commuting there was an older subaru I always
| parked near in the parking garage that, whenever I unlocked
| my newer subaru with my fob, it's alarm would go off. I sat
| there one day and did it over and over again, so it was
| definitely casual.
| fullstop wrote:
| "Fixed" in the same way I can "fix" a stuck key on a keyboard by
| physically removing it. They've circumvented the problem but are
| left with less than what they originally had.
| bonestamp2 wrote:
| Ya, keyless entry/start is a huge convenience. I'd be mad if I
| had to disable those features to use my car.
| WillPostForFood wrote:
| This is a like a metaphor for modern life with technology
| parasitically draining time and energy from humanity with shit
| apps and buggy software while the "mechanics" refuse to even
| acknowledge there is a problem.
| jimmytucson wrote:
| I had a similar problem with a Silverado. It is very annoying.
| When WFH started and I stopped driving every day, I had to jump
| the battery seemingly at least once a month.
|
| I had people tell me it was the battery - I knew it wasn't
| because I had replaced the battery a few times due to the
| parasitic draw emptying it over and over and wearing it out. I
| took it to a trusted mechanic and they told me they didn't want
| to fix it. I pulled all the fuses myself, one-by-one, and never
| figured out which one was the problem.
| localhost wrote:
| While not a fix for this problem, a nice form of insurance is a
| Lithium Ion jump start battery[1]. I'm amazed that a hand-held
| battery can discharge fast enough to jump start my car, but ...
| it works great.
|
| [1] https://www.amazon.com/dp/B0B55RFM1Z
| insane_dreamer wrote:
| > Dealer: said my car was fine and returned it to me. My car died
| the next morning.
|
| Least surprising finding
| legitster wrote:
| I feel pretty handy with car repair stuff, but "intermittent
| electrical problems" are the absolute worst. In this case they
| were pretty lucky to trace it to a specific module. You have
| miles of cables in a car and and most of them are completely
| inaccessible. There are never any fun, happy, clever
| troubleshooting stories. You always feel robbed of your time.
|
| This isn't a new problem either - ask anyone who tried dealing
| with a British roadster. It's also why I stay far away from used
| cars with aftermarket accessories.
| swamp40 wrote:
| New Mechanic: _Low battery is causing your low battery_
|
| Ok, thanks.
| zwieback wrote:
| Not just for highly computerized cars, I have a 97 Ranger where
| literally everything is manual and I don't even have a dome light
| anymore. There's a parasitic drain I can't quite figure out so I
| just make sure to start it every once in a while. Since I'm a
| year round bike commuter the truck can sit around for a long
| time, especially in winter when there's no house and garden
| projects. I've considered adding a manual battery disconnect, the
| only thing I'd lose are the pre-programmed radio stations.
| Scoundreller wrote:
| Solar panel? Depends how big the draw is.
| mbfg wrote:
| South Main Auto has an excellent youtube channel with various
| parasitic draw videos. For those struggling, it's a good watch.
|
| Here's one such: https://www.youtube.com/watch?v=qDqlG5bRq8k
| grokx wrote:
| In the 00s, my dad had an issue with the infotainment system of
| its Peugeot 407 that would no longer boot.
|
| An official Peugeot mechanic told him that it would cost
| something like 4200EUR to replace the unit, so he asked me if I
| could have a look.
|
| After a quick search, I found an update for his system, burn it
| on a CD, and put the CD into its car.
|
| The system updated, and then would work normally. Problem fixed
| for one hour of my time and a CD.
| Scoundreller wrote:
| A lot of dealership mechanics are mindless flowchart followers
| that aren't even allowed to use their brain.
|
| Though I'm surprised "update" wasn't a part of that official
| flowchart.
|
| Have had dealership mechanics ignore my notes and identify a
| part as being failed despite my method of 100% excluding that
| part as being bad.
| ciscoriordan wrote:
| I had a parasitic drain on my Tacoma from my Automatic device
| (OBD-II reader / GPS tracker). I parked in a garage with no cell
| service and it drained the battery by constantly trying to
| connect. It was a non-issue when I commuted daily but started
| killing the battery when COVID happened and I switched to WFH.
|
| Hard for mechanics to diagnose because they had no idea what that
| device was and also one of their first steps was to unplug it,
| put it in a cupholder, and plug their own OBD-II reader in.
|
| Now the Tacoma is parked again most of the time because I got a
| Tesla and I'm noticing a voltage drop. I need to do more
| research, I don't know if this is normal for being parked or if
| there's a drain.
| williamDafoe wrote:
| We have a similar problem with a Lexus rx300 2001. The computer
| never goes to sleep. I was thinking of looking for (or making) a
| patch-fuse with a kill switch to stop the drain. Computer sleep
| depends on the flakey door controller switches.
| antiquark wrote:
| I solved this problem on my Dad's car by installing a mechanical
| knife-switch on the battery terminal. Anytime it's going to be
| parked for more than a few days, I pop the hood and disconnect
| the battery.
| l00sed wrote:
| I did a write-up when my car battery died on the way to fish fry.
| Testing for parasitic draw is no fun. https://l-o-o-s-
| e-d.net/car-hacking
| KingMachiavelli wrote:
| I've never understood why cars don't just cut power before the
| battery is too low to start. If that's too complicated then just
| have an option to cut all power after X hours of non-running
| time.
|
| I bet the old popular theft of car radio is a root cause; cars
| needed to stay running to keep the alarm active and power the
| radio continuously so it wouldn't require the unlock code every
| time you start the vehicle.
|
| It's actually pretty impressive how much power even a 200mA draw
| at 12V is over a few days; it's about 58 Watt-hours or 3.5 iPhone
| batteries per day.
| pvaldes wrote:
| > why cars don't just cut power before the battery is too low
| to start.
|
| Some cars computers block the start by software if the battery
| is "slightly" low (even if would not be too low to start).
| bonestamp2 wrote:
| Cutting the power is easy, the hard part is for the car to know
| when/how to reconnect power when the driver wants to start the
| vehicle. I guess with a physical ignition switch, the
| mechanical motion of the tumbler could reconnect power. But,
| most cars don't have ignition tumblers anymore.
| topspin wrote:
| > I've never understood why cars don't just cut power before
| the battery is too low to start.
|
| The design of most cars can't tolerate losing 12V DC power
| without problems. Clearing superfluous codes after a battery
| swap is SOP. Cars are build for two simultaneous customers:
| regulatory regimes and work-a-day 13.5K miles a year workers
| that start (and thus charge) their cars at least every 48-72
| hours. Other use cases aren't really considered.
|
| Some are better than others though. I have a 21 year old Nissan
| with a factory alarm and key fobs that sits for a month or more
| and starts fine every time. Heating helps a lot.
| sixstringtheory wrote:
| Hah. I've replaced the battery in our Subaru Outback on average
| once per year, which is way too high for this environmental
| minded person.
|
| I just went out last night to grab something from the car and it
| was making a loud electrical whirring noise. I had driven it
| several hours prior, no idea how long it had been going. I
| recorded a video and it is clearly audible. I started it and
| turned it off again, and the noise stopped.
|
| Friend of mine (and several other commenters here) has an old
| pickup with a switch on the steering column that cuts the circuit
| at the battery, I'm ready to install one on both my cars.
| jakestl wrote:
| Same here, 2018. Last battery replacement was 6 months, let's
| see how long this one lasts.
| sevenf0ur wrote:
| I would check your owner's manual. Mine says not to be alarmed
| about noise coming from under the truck. In my case it's a fuel
| evaporation check.
| wisosim wrote:
| That whirring noise is likely from the EVAP system of your
| Subaru. See below threads for more info about it. Having to
| replace your battery once per year is not normal though so
| there is definitely something else going on.
|
| https://www.clubcrosstrek.com/threads/buzzing-sound-from-pas...
|
| https://www.subaruxvforum.com/threads/whats-that-sound.14672...
| anamexis wrote:
| Ugh, I've also got an Outback (2019) with a regularly dying
| battery. Let me know if you ever find any leads on the root
| cause.
| sixstringtheory wrote:
| One was a PEBCAK that I personally consider a design flaw:
| the rear gate light switch is on the ceiling at the opening
| of the gate (on our 2016), and the "on" position is activated
| by moving the switch outwards, ie towards the back of the
| vehicle. It had been inadvertently dragged into "on" position
| while unloading bikes, rafts and other outdoor gear, and then
| killed the battery while we were out for a couple days.
|
| Didn't realize this was happening until returning to a
| drained battery on two occasions, and then observing the
| effect later while doing some garden work, when I finally
| connected the dots. I've since duct taped it into the "off"
| position.
| ninjanicely wrote:
| I have a 2019 Outback as well. I just went through some
| battery dying issues. Took it to the dealership, they said
| that the Onstar module (after 2-3 years) will start to
| malfunction and create a parasitic drain.
|
| The only fixes they have (as of a couple weeks ago) was to a)
| buy a new module (which are on back order because a number of
| peeps are having this problem) -- which will eventually break
| because they haven't reengineered it. b) disconnect the
| Onstar module via a circuit (my tweeters are on the same
| circuit, so I'd lose them) c) Open up the center console and
| only disconnect the Onstar module.
|
| I opted for C (which I was charged an hour of labor for). The
| tech there said to check back in every few months to see if
| Subaru puts out a new module that fixes the issue.
|
| Edit: The tech told me the Onstar module was a specific issue
| with 2019 Outback/Legacy, and that 2018 and back doesn't have
| that problem and in 2020 they redesigned the whole model, so
| the newer ones don't have that issue.
| skittlebrau wrote:
| I have the same issue, seemingly, with my 2017 Outback. My
| battery kept dying for which I got a lot of run around from
| the dealer (gaslighting about keyless entry drains it if
| the key is too close to the car, etc.) Eventually I found a
| Reddit post about the DCM (Starlink) module, removed this
| fuse, and it hasn't died since. It sounds like it wakes up
| in the middle of the night to do something and thereby
| drains the battery, so whenever they test at the dealer for
| extra drain, they find nothing. Having that fuse out kills
| some speakers and the mic too, so it's a kind of annoying
| solution. I have not gone back to complain again recently
| though, so maybe they can do whatever it is they did for
| you. I saw some posts about wiring it to another circuit
| that's off when the car is off, but I am not confident
| doing that myself.
| Captaffy wrote:
| Had the same problem recently with a 2011 Mercedes. Didn't figure
| it out until eventually the Keyless Go module (which allows push
| to start and automatic door unlocking) died. This fixed the
| parasitic drain.
|
| Apparently when these sorts of modules are dying they fail to
| turn off and drain the battery by constantly searching for the
| key fobs. Incidentally while the battery drain was going on the
| key fob batteries were dying extremely quickly as well, also
| suggesting a lot more communication than normal was occurring.
| jws wrote:
| I have failed to find the parasitic draw on an RV (slower than
| this one, it takes a couple weeks to kill the battery). I finally
| got a "Top Post Battery Master Disconnect Switch", which is a
| little dinglebob that goes between the battery post and cable and
| lets you easily break the circuit. I highly recommend the $12
| solution for an intermittently used vehicle.
| rootusrootus wrote:
| > RV
|
| I'm reminded how often people come to the RV forum trying to
| figure out parasitic draw. The answer almost always ends up
| being the propane detector. People forget it's even there.
|
| Less of an issue on newer RVs that come with at least one basic
| solar panel installed from the factory.
| pugworthy wrote:
| Probably not an issue with more modern systems with solar
| panels and the detector on the house batteries.
| driverdan wrote:
| Very few RVs come with solar.
| driverdan wrote:
| I'm surprised it didn't already have a master shut off switch
| next to the battery. You should always shut off / disconnect
| the battery when not in use because, as someone else pointed
| out, the propane detector will drain it.
| bombcar wrote:
| You can also grab a trickle-charger and use that when it's at
| rest, which can (on modern vehicles) prevent the computer from
| going nuts.
|
| If you're fancy, you can even make it a quick-disconnect setup
| so that if you drive away with it still on, it won't break
| anything (or do the poor-man's version where you have the wire
| connected to the wheel chocks).
| hirundo wrote:
| I installed a battery disconnect switch on the dashboard of my
| jeep. There's a spot that seems made for it. It was a $27
| solution, but I don't have to pop the hood. And it solved my
| charge parasite problem instantly.
| overthrow wrote:
| I thought about this but the problem with newer cars (mine at
| least) is killing the power wipes the memory so it won't pass
| an emissions check (or something like that). After my battery
| died I had to find an excuse to drive an extra 100 miles so I
| could pass emissions.
|
| On my car the emissions laws definitely _caused_ more emissions
| than they saved that day.
| ksherlock wrote:
| I once had a car where I had to disconnect the battery to
| clear the check-engine light so it _would_ pass a state
| inspection.
| stuff4ben wrote:
| That usually doesn't work anymore as mechanics can tell
| that you've done that when hooking up the ODBII port.
| jxramos wrote:
| I recently noted in my OBD2 scanner that some vehicles
| support the measure of miles since check engine lights
| were cleared or something to that extent. It made me
| ponder at some point in the future there is going to be
| regulation mandating that to pass an emissions test you
| must pull up to the test station with a minimal threshold
| mileage on the car to vet no check engine lights have
| tripped in that interval.
| linuxftw wrote:
| That's already a thing. Many sensors will be in 'learn
| mode' and you can't pass emissions until they are fully
| active.
| sidewndr46 wrote:
| I hear this all the time, but I have never understood it. If
| I clear my drive cycle monitors, they are all passing again
| just a few miles later. Do some vehicle manufacturers just
| put insane constraints on the drive cycle monitors?
| etrautmann wrote:
| That seems reasonable since anyone could clear and tune an
| engine with minimum effort to pass emissions without a
| history requirement.
| sokoloff wrote:
| There is a drive cycle set of requirements and it's usually
| possible to clear them in under 20 miles. Trying to figure
| which part of the cycle isn't accomplished yet is the
| challenge. I've chased it down on my wife's Honda when we
| were trying to get it to go "Ready" the same afternoon.
| Usually just not doing anything unusual for a day or so of
| normal use is enough, but you can often query the OBD2
| system to get the portion of the cycle that's not yet
| complete. Just doing a long highway drive isn't going to do
| more than a moderate highway drive already did.
| londons_explore wrote:
| > Do some vehicle manufacturers just put insane constraints
| on the drive cycle monitors?
|
| Yes. Combine with the fact some only pass after certain
| conditions (eg. over 3000 revs for 10 mins, or idle for 5
| mins, or only after 3 starts, only when the outdoor
| temperature is within this range, etc). Sometimes those
| conditions aren't stated in the manuals.
|
| That makes the checks passing seem more like a random
| process and driving more will usually make them pass,
| eventually.
|
| And drivers without a code reader won't know when it has
| passed, so they are usually instructed by mechanics to
| drive a long way to be sure before taking it in for a test
| (don't want to have to reschedule the test just because you
| didn't drive it enough).
| Scoundreller wrote:
| And some jurisdictions will pass some "not ready" codes
| because a proper cycle may not happen for months.
|
| A code reader really pays off sometimes to reset
| everything :)
| ceautery wrote:
| This is type of thing I've seen Eric O. over at South Main
| Auto[1] fix in dozens of videos. Mad troubleshooting skills,
| works hard to find root causes of things. He's pretty amazing,
| hidden away in some no-account town in upstate NY.
|
| 1 - https://www.youtube.com/@SouthMainAuto
| gooseyard wrote:
| I really enjoy his channel- another good one is the Pine Hollow
| Auto Diagnostics channel, which has dozens of really involved
| parasitic draw diagnoses, have learned a great deal from that
| one.
| bityard wrote:
| Although I perform as much of my own auto maintenance as I can,
| I watch Eric O because he's entertaining, and all of the
| technical wisdom and advice just comes along for the ride.
| bruiseralmighty wrote:
| My current driver is a pre-2010 vehicle. I really don't want to
| buy any of these newer cars. Maybe I can import one from Cuba.
| matt-attack wrote:
| Couldn't he have just measured the resistance of the fuse to
| determine the current flow? He knew the voltage drop.
| irrational wrote:
| >Sometimes I wanted to pretend the problem didn't exist more than
| I wanted to fix it.
|
| Story of my life.
| abosley wrote:
| I sold my MazdaSpeed 3 due to a parasitic drain - it was at the
| dealership for 4 months at one point - with no resolution.
| maherbeg wrote:
| Well this is entertaining. Our 2012 Mazda CX-7 seems to die if we
| don't drive it for a week. I've sort of ignored this problem but
| now I'm going to go check some fuses and see if this is the same
| problem.
| Gordonjcp wrote:
| I found that my old (1997) Range Rover would flatten its battery
| after being parked outside my house over a weekend. If I didn't
| drive it for two or three days, it would be too flat to start.
|
| It turns out that the BECM (body ECU) wakes up from sleep if it
| hears anything coming in from the RF keyfob receiver, on
| 433.92MHz, a standard ISM frequency. If it's not a valid fob code
| (and there is a surprisingly complex rolling code sequence) it'll
| go back to sleep after 20 minutes or so.
|
| The oil tank gauge for my central heating had a remote sensor
| that... yup. Transmitted on 433.920MHz, of course.
|
| The aerial for the keyfob is on the rear right corner of the
| vehicle, the oil tank for the heating was on the left-hand side
| of the driveway right at the back of the house, so when I backed
| into my driveway it was right beside the receiver.
|
| I managed to do just fine with popping the lid off the oil tank
| once a month and looking inside to see how much fuel was left,
| having taken the battery out of the tank sender.
| 83 wrote:
| Can't recall where, but I recently learned this was a common
| issue at airports in the early days of wireless key fobs. The
| radar sweep at the airport would wake up the receivers causing
| cars parked there for a while to have dead batteries.
| civilized wrote:
| My wife and I gave our old car to her parents. In the subsequent
| years, its battery kept dying and we had to go over to their
| place and jump it. Never happened in the prior 7 years we'd owned
| the car. The mechanic said nothing wrong with the battery, but
| suggested there might be a parasitic drain somewhere.
|
| A few days later, we were visiting them. I looked at the car and
| saw the door closed, but not properly latched and ever-so-
| slightly ajar. You know, that half-closed thing car doors do when
| you don't close them hard enough.
|
| It turns out someone, possibly my son, had been not closing the
| door completely. This did not keep the lights on or cause any
| other visible sign, as it would in some cars.
|
| After I told them to slam the door fully shut, never a problem
| again for 2 years and counting.
| adversaryIdiot wrote:
| Thats insane... To consistently not close the door like that
| civilized wrote:
| I know, I'm at a loss. The kid slept in there a lot - maybe
| they were trying to shut it quietly to not disturb him?
| WirelessGigabit wrote:
| My car beeps loudly and angrily at me if the doors are not 100%
| closed when I hit the close button on the fob.
| gengkev wrote:
| With my car, trying to lock the doors just doesn't work if
| one is left open -- not always the most obvious failure mode,
| but it's been enough to get me to notice something's wrong.
| mysql wrote:
| I used to be a computer engineer working on embedded systems for
| automobiles. Quiescent current is what the normal proper draw is
| called for these systems when the car is off. We worked very hard
| getting these numbers in spec but it was hard to catch everything
| especially in this case where the issue is probably due to
| software missing the sleep state for that module. This could be
| from bad code or your CAN/LIN bus is messed up in your car. 99%
| of mechanics (and engineers) have no idea where to start with
| debugging these issues and the answer will be "replace the
| module".
| xattt wrote:
| > This could be from bad code or your CAN/LIN bus is messed up
| in your car.
|
| If the car had been operational for years and years, why would
| bad code crop its head now?
| toast0 wrote:
| Some counter finally overflowed. And now the new value is
| less than the old one, which breaks something, etc, etc.
| overthrow wrote:
| Well this is timely. I have a parasitic draw on my NC Miata. The
| first mechanic just replaced the battery. The second told me it's
| normal for the battery to die if you don't drive it for 3 days
| (because "cars have computers now"). It seems like mechanics
| really don't like digging into the electrical part of the car...
| but these days that encompasses more and more of what can go
| wrong.
|
| Without time to dig into it myself I've just been parking it with
| a battery tender every time I come home.
| lylejantzi3rd wrote:
| > It seems like mechanics really don't like digging into the
| electrical part of the car...
|
| Tell me about it. I'm in a similar boat. My audi a4 has had a
| parasitic draw for the past 10 years. My mechanic didn't want
| to take the time to address it because that sort of thing takes
| a serious amount of time and he's always backed up. I got out
| my fluke and narrowed the cause to what I believe is the
| comfort control unit. I can't replace it myself because it's a
| coded part. My mechanic won't do it because he won't confirm
| that's the cause.
|
| None of the other mechanics in my area have the equipment. Even
| the Audi dealership won't touch it because they're backed up
| too. So, I keep a battery jumper in the glove box and hook the
| battery up to a tender when I can (outdoor parking).
|
| I don't know what I'm going to do for my next car. Pretty much
| every car made after 2010 has coded parts and are more computer
| than mechanical. It does make me tempted to learn the
| electronics part and open a garage that focuses specifically on
| fixing electronic issues in modern cars.
| Eumenes wrote:
| I'm looking into buying a reliable older vehicle, pre 2000,
| and just rebuilding the engine
| ilyt wrote:
| If car is at the point of engine rebuild you'd probably
| have to replace half of the suspension too
| bronson wrote:
| At least! When my engine finally needed a rebuild, so did
| the transmission, steering box, CV joints, and center
| differential. And you're right, it needed new bushings,
| shocks, springs, and balljoints.
| dsfyu404ed wrote:
| "need" starts being a very subjective word when talking
| about some of these components at high milage.
| Baeocystin wrote:
| I drive a 1998 Jeep Grand Cherokee. I get asked if I'm
| interested in selling it at least once or twice a month,
| nowadays. The sightlines are amazing compared to modern
| cars, its AC is OP, and the AMC 4 liter straight six is one
| of the most durable car engines ever made. Mileage is not
| great, but it's paid for and dirt cheap to insure, that
| buys a lot of gas right there.
| mikrotikker wrote:
| Inline 6 has to be one of the best engines. I got 3 cars
| with them in 4L, gas injected, gas carbureted and diesel.
| They go so well.
|
| The only computer in the diesel one is the glow plug
| timer and there is no computer in the carbureted one
| (both 1991 Nissan Patrols).
|
| The injected one is a 2005 ford falcon and is starting to
| get all sorts of interior electrical niggles. Only wiring
| issues in the patrols is a left headlight short which was
| easily routed around using relays.
| sokoloff wrote:
| > My mechanic won't do it because he won't confirm that's the
| cause.
|
| My experience is that a lot of independent mechanics will do
| what you ask them to do, so long as they think it's not
| unsafe and have confidence that you'll pay the bill without
| complaint when the task is done whether or not the problem is
| fixed.
|
| Probably not a good "this is my first time meeting you, but
| please replace my flux capacitor" but if you've got a history
| with the shop, I'm surprised you couldn't talk him into it.
| (I worked in a shop briefly in college. We'd do what the
| customer wanted, including installing parts they bought, but
| the only warranty was on a "we spent an hour; you paid for an
| hour; thus ends the transaction" basis.)
| HeyLaughingBoy wrote:
| Yes. I had a problem with a leaking transmission once and
| the shop refused to accept my diagnosis because "in all my
| years servicing transmissions, I never heard of that
| failing."
|
| Finally, the service manager agreed to check it out with
| the understanding that if I was wrong, I still had to pay
| for the time they spent investigating.
|
| I was right :-)
| leetrout wrote:
| This was me with a Suzuki vstrom with a bad solenoid.
| Mechanic ran 12 volts through it on the bench and refused
| to accept it wasnt working in the bike.
|
| Bought my own solenoid online and surprise the bike
| started working again.
| sixothree wrote:
| > Even the Audi dealership won't touch it because they're
| backed up too.
|
| Getting an appointment at my Audi dealer is always 6+ week
| minimum wait. I don't think I've ever dealt with a dealer
| this consistently backed up. And my issues have been recalls
| and brake problems; but simple oil change is a similar wait
| time.
| addisonl wrote:
| Probably should get a brand more reliable than Audi...
| BoorishBears wrote:
| I hear people say that about my BMW, and realistically the
| hassle of some reliability issues is nothing compared to
| driving the lifeless husks of cars they recommend instead.
|
| (there are reliable sports cars, but it significantly
| limits the pool you can select from)
| cramjabsyn wrote:
| I like Mazda and Honda (in that order). Japanese
| reliability, sporty handling and a turbo engine for a
| fraction of the german cars.
| Scoundreller wrote:
| I feel like I've lucked out in life with an '08 6MT N52
| e90 and an '05 Corolla with a 1ZZFE.
| vGPU wrote:
| Agreed. I beat my C5 and C6 pretty hard, but aside from
| (some) of the GM/F cars you're very limited in choice.
| Especially if you're looking for a lightweight sedan.
| legitster wrote:
| That's fair, but it's funny because that's how I always
| felt about BMWs. My buddy loves them but I always felt
| like they were so... sterile. Unless you are at a track
| or love cutting off people in traffic it feels really
| hard to have any fun in one.
| BoorishBears wrote:
| > My buddy loves them but I always felt like they were
| so... sterile.
|
| I'd love to know which specific model you found sterile
| (wouldn't happen to be some 4 cylinder would it?)
|
| People who drive boring cars love to parrot magazine
| reviewers... not realizing their definition of sterile is
| relative to a 911, not their Accord.
|
| > Unless you are at a track or love cutting off people in
| traffic it feels really hard to have any fun in one.
|
| I track my cars, but it's not hard to enjoy pleasant
| driving dynamics without resorting to being an
| irresponsible driver in a well-sorted car.
|
| I'll defer to you on how fun cutting people off in
| traffic is though?
| vGPU wrote:
| Agreed - the last 5 that felt good to drive was the e39,
| and the rest probably peaked with the e90 or e8x. I felt
| the same way with the corvette - my c5 was the most fun
| to drive. C6 was an upgrade in comfort but significantly
| number, and the C7 was horrific. I took a C7Z for a spin
| and it felt slower and more boring than my c5 despite
| having 2x the HP.
| JPws_Prntr_Fngr wrote:
| Sterile compared to what? Is there another manufacturer
| of acceptably-tuned rear-drive sedan chassis out there at
| a semi-reasonable price point that I should know about?
|
| (I'm talking about pre-2010 BMW here; I would totally
| agree with most new ones being sterile)
| legitster wrote:
| I mean, I guess if you are limiting yourself to that
| exact style of car then yeah I guess.
|
| (Although the Mazdaspeed6 was 90% of a BMW with 10% of
| the maintenance bill).
| throwawayf37jg wrote:
| I agree it may be 90% as fun to drive (which is
| subjective), but you're comparing FWD to RWD. I'd much
| rather have a 80's-90's Nissan or Subaru, especially
| built, than a modern BMW, though. Much more soul in
| vintage cars imo. Some vintage BMWs were pretty reliable,
| a lot of modern Nissans have awful reliability.
| johncalvinyoung wrote:
| As a current owner of a 90s Jaguar and an 05 Volvo, I've
| been looking at low-mileage E90 era BMWs for my next
| daily driver. Not too scared of moderately expensive
| maintenance, but would like it to be more reliable than
| the Volvo has been.
| addisonl wrote:
| Sounds quite anecdotal.
| [deleted]
| JohnFen wrote:
| I wonder if installing a switch to disconnect the car's
| battery entirely would be an acceptable (but obviously hacky)
| solution.
| pvaldes wrote:
| That would depend on the car brand. Not so good idea in
| some brands.
|
| Assure to write somewhere your radio code password first.
| somat wrote:
| Not really, When powered down(battery diconnected) the
| computer then has to re learn parameters/pass internal
| validity checks. On a well preforming system this will be
| done in as little 1 or 2 rides but on a marginal system
| this can take many rides. the computer may not enter closed
| loop mode until these checks pass.
|
| closed loop mode is where the computer set it's output
| values(fuel air ratio, timing etc) based on it's input
| sensors. open loop mode is where it sets it's outputs on
| known safe working values, but it may not run particularly
| well. i think this is related to the so called "limp mode"
|
| Note My knowledge on this subject is very out of date. I
| had to figure it out for my old 2001 car. Newer vehicles
| may actually have flash storage and the computer parameters
| survive power out.
| m463 wrote:
| I did this with an old vehicle taht was pretty basic
| without a lot of electronics.
|
| the actual problem was sort of electronic-releated - leave
| lights on, drain battery to zero.
|
| I put on a battery-cutout-monitor-thing. If battery drained
| to x%, it would disconnect the battery. to start the car, I
| think you had to stand on the brake pedal (add a load -
| like brake lights?) and it would reset and reconnect the
| battery - then you could start it.
| lylejantzi3rd wrote:
| This isn't a good idea for an Audi. The computer doesn't
| like going without electricity. It runs a bit rough for a
| day or two afterwards and sometimes will "forget" how much
| gas is in the tank.
| tonyarkles wrote:
| Some newer vehicles get upset when you do that, but older
| ones generally don't. You may lose radio programming
| though. I've got an old '95 Caravan that's going to be
| getting a quick disconnect like this one pretty soon
| though; the drain takes a few weeks to kill the battery,
| but we don't drive it very often either. Why do we still
| own it? With the back seats removed, you can easily put
| 8'x4' sheets of plywood in it.
| fossuser wrote:
| If you're going to have to deal with it might as well get a
| tesla which is at least all in on the electronics and the
| company understands software.
|
| The dealership model has really been awful for legacy
| manufacturers.
| jimnotgym wrote:
| Good luck in 5 more years when Tesla decide that your car
| is now unsupported.
|
| I wonder if the Tesla mechanics are measurably better than
| the franchise dealers? I doubt it. I bet they have fancy
| testers, but when the tester is not showing 100% the right
| answer I doubt they are any use at all.
| Nifty3929 wrote:
| What are coded parts? I spent a minute googling and couldn't
| come up with anything that seemed right.
| jobead wrote:
| I believe this means that the part's computer has the
| vehicle's VIN loaded into it with a computer that can only
| be purchased/used by a certified technician. If he was to
| buy a new part, it would have a blank VIN; and if he pulled
| one from a junker, it would have that car's VIN.
|
| (edit: should also say, I think a VIN mismatch would cause
| the ECU to refuse to work with that part and shut down)
| Nifty3929 wrote:
| Well that's dumb. I've never heard of that before. But I
| guess I shouldn't be surprised. Thanks!
| nickff wrote:
| The problem with specializing in these issues is that most
| customers will be dissatisfied when you charge them thousands
| of dollars to reset a minor module on their car.
|
| How many hours of shop time are you willing to pay for with
| no guarantee of a solution, and very few (if any) parts
| replaced?
| jopsen wrote:
| > How many hours of shop time are you willing to pay for
| with no guarantee of a solution, and very few (if any)
| parts replaced?
|
| Imagine opening a computer software support business where
| you bring in your old proprietary binary programs that you
| got from who knows where, and the business is to fix bugs
| you've found.
|
| Maybe some really big enterprises would pay for that sort
| of thing. But I doubt it would be feasible for consumer
| stuff.
|
| It would be a crazy/fun kind of business to run. I'm sure
| it probably exists.
| acapybara wrote:
| That actually sounds like a great business idea.
|
| Bug Hunters
|
| Extremely valuable service. I bet there'd be a lot of
| demand.
| [deleted]
| peteradio wrote:
| Dude's been tending his issue for a decade, I bet he'd have
| at least those like him as a customer. In a metro he might
| have a pretty lucrative business. On the other hand in the
| metro there is probably someone who already does this work,
| but they are very hard to find!
| jopsen wrote:
| How do potential customers find your specialized shop?
|
| Most people will give up, stop researching and buy a new
| car when the dealer tells them it can't be fixed.
| yurishimo wrote:
| Word of mouth w/ cars is hugely important. Anybody with a
| good mechanic will tell you about them.
|
| Shoutout to "The Hondew Shop" in Dallas. He does great
| work on all Honda/Acura products!
| cwillu wrote:
| If you can identify the fuse for the unit, it might be less
| annoying to pull it when parking rather than hooking up a
| charger.
| ssharp wrote:
| I wired in an aftermarket DVD player in an old car and
| tapped into a fuse that was supposed to not draw power when
| off. Of course, it did draw power so the DVD player never
| shut off. It wasn't too much of a draw but I didn't want to
| end up with a dead battery situation because of it so my
| solution was to just plug the fuse tap in when the kids
| were in the car and wanted to watch something.
|
| I'm sure there was a more elegant solution (find a
| different fuse, rig up a button, etc.) but this was the
| path of least resistance and wasn't really annoying to do.
| aidos wrote:
| "path of least resistance" is very fitting.
| Freedom2 wrote:
| Definitely a cool, new term! Thanks to the GP for
| introducing it to my lexicon.
| hutzlibu wrote:
| You also might enjoy this joke then:
|
| https://i.pinimg.com/originals/a4/c5/bb/a4c5bbd867b819a68
| 7ea...
| acapybara wrote:
| WiFi arduino + disconnect relay on the battery.
|
| Completely disconnect battery when not in use.
| lylejantzi3rd wrote:
| That's a great idea. I can't believe I didn't think of
| that. Thanks!
| dn3500 wrote:
| If it were me, I would pull the fuse, then jumper the
| block over to a different fuse on a circuit that is off
| when the ignition is off. Then you never have to think
| about it again.
| asciimov wrote:
| They also make switches for fuses, so that you can kill
| the circuit without pulling the fuse.
| elteto wrote:
| If you are going with a hack then _this_ is the way to
| go.
| jessaustin wrote:
| Pulling fuses is a pretty reliable way to _find_ the
| relevant fuse in the first place. If the battery doesn 't
| run down while a particular group of fuses is pulled, the
| one you want to pull is in that group. Start with half
| the fuses, then narrow down.
|
| You might have to reprogram your radio channels...
| bityard wrote:
| I can recommend searching for "South Main Auto parasitic
| draw" on YouTube. The guy is a genius at electrical
| troubleshooting.
|
| His strategy isn't to pull fuses, it's to set the car sit
| for at least 30 minutes or so (with key off) and then
| check each fuse with a multimeter to see which has
| current on it, and then check everything on that circuit.
| Arm yourself with schematics and wiring diagrams,
| otherwise it'll end up being something of a wild goose
| chase.
|
| (The idea being if you start pulling fuses, you can
| "reset" various computers in the car, which may show up
| as a false positive. It can take up to 30 minutes or so
| for all the various computers in a car to all go to
| sleep, although it's usually only a few minutes for most
| cars.)
| jessaustin wrote:
| It would take someone more skilled than I, or with better
| tools, to check current in a fuse box without removing
| fuses. Maybe I should watch that guy and get better...
| pvaldes wrote:
| A multimeter is cheap and really easy to use. This is the
| safest way also
| gridspy wrote:
| You measure the voltage across the fuse. Then you look up
| the fuse's resistance in a datasheet. Current is Voltage
| / Resistance.
| MaKey wrote:
| AFAIK the fuses have contact points you can use to
| measure the current.
| cwillu wrote:
| You can check continuity across the contact points, but
| measuring a 75mA current via the voltage drop across a
| 0.0034ohm resistance (give or take) means reading 0.2mV,
| which is... borderline for a consumer multimeter.
| bityard wrote:
| > It seems like mechanics really don't like digging into the
| electrical part of the car.
|
| That is certainly correct. Troubleshooting electrical issues
| takes a different set of skills than most mechanics are trained
| to deal with. Most mechanics are so busy that throwing parts at
| a problem is the best way to deal with issues where the cause
| isn't readily apparent. It's not worth their time to really dig
| into a difficult issue because if they spend 8 hours of shop
| time and try to bill that to a customer, the customer is going
| to just balk anyway. Better to throw a part at it, bill 1.5
| hrs, send it out the door, and let the next guy deal with it.
| And then move on to some more profitable muffler and brake
| repair jobs.
|
| This is thankfully not ALL mechanics, but it certainly is a
| large percentage of them, IMO. (Yep, even dealerships.)
| amtamt wrote:
| This sounds like a majority of software engineers (and their
| direct managers) asking to add more CPU and RAM, when
| software is slow, instead of analysing a problem.
|
| I guess mechanic's time is more valuable than parts.
| matt_s wrote:
| Imagine as a software developer you tracked your time working
| tickets, your pay was hourly, and depending on the ticket type
| you were prescribed how long that ticket should take and paid
| those set hours whether you went over/under the set hours. This
| sounds completely insane but this is how car mechanics work (as
| I understand a lot of shops do this). Replacing a battery might
| be 1/4 hour labor, replacing brakes on car model XYZ is 1.25
| hours, etc. This is why mechanics won't really want to spend
| time on issues like this. It could be a wild goose chase
| tracking down every electrical sub-system in the car only to
| find something chewed thru a wire somewhere under a panel. The
| fix might be $15 in parts and 20 hours of actual labor but
| their system might quote replacing a wire as 1 hour labor.
| winrid wrote:
| That's kind of how dealer mechanics work but not any other
| mechanic... They work for 10 hours, you get billed for 10
| hours.
| jonfw wrote:
| Many shops work by book time, not just dealers, although
| obviously YMMV based on the shop and the work.
|
| It's more common for routine maintenance to be charged by
| book time since it's a standard procedure, less common for
| more complicated issues
| micromacrofoot wrote:
| I've been to multiple mechanics, talked to roadside assistance
| people, posted in multiple forums, and talked to family about
| this problem with an old car of mine... and they all swore up
| and down that you should start a car if it sits longer than a
| weekend, maybe a week tops. They made me feel insane about it,
| it's one of those widely accepted things that's just not true
| most of the time.
| pengaru wrote:
| > It seems like mechanics really don't like digging into the
| electrical part of the car... but these days that encompasses
| more and more of what can go wrong.
|
| Having worked as a mechanic in my youth, and worked as a
| software engineer in SV, the kinds of troubleshooting skills
| and detail-oriented attention span involved in diagnosing these
| issues are far more common in the latter than the former
| industries.
|
| My impression is it's rare for someone with such abilities to
| stay a mechanic, they can earn far more money in tech, with
| less exposure to hazards.
|
| On the subject of mechanics failing to diagnose electrical
| issues, I have my own story too:
|
| Decades ago, back in IL, a friend inherited a low-mileage
| minimalist Ford Escort hatchback, manual trans, crank windows,
| it was a great little econobox to inherit, on paper. He kept
| having the battery die on him. Not being a mechanic or even a
| hobbyist gearhead himself, he kept bringing it to shops. They
| replaced the alternator, the wiring harness, the battery, the
| starter, they just kept throwing parts at the car. This is what
| most "mechanics" do nowadays; a poorly informed process of
| elimination via new parts, on your dime.
|
| I hadn't been in contact with this friend for years when I
| heard about this "cursed" low-mileage car sitting in his
| garage, full of new parts with invoices totaling well over $1k.
| He was car-less at the time because of this situation. I
| offered to fix it for him, but he didn't have any confidence
| left in the vehicle or my ability to fix it, he was
| understandably fatigued by the whole thing. So I offered
| something like $250 and took the car off his hands.
|
| 15 minutes with a voltmeter revealed a huge voltage drop across
| the negative battery terminal and the chassis. Followed the
| negative strap to where it attached to the chassis and the area
| was corroded (recall it's an IL car). Removed the rusty bolt,
| wire-brushed the unibody steel behind it, the bolt and cable
| lug, slapped dielectric grease on everything and reassembled.
|
| The car charged the battery fine and ran like a champ. I ended
| up selling it back to him a year or two later for basically
| what I paid plus a few hundred for my trouble/towing etc. He
| wouldn't even take it back until I had driven it for years to
| prove it was fixed. It was _that_ brutal an experience for him,
| dealing with "expert" "mechanics" bleeding him dry.
| brewdad wrote:
| Don't ever go back to that second mechanic.
| ilyt wrote:
| At the very least you know to which 2 mechanics you should
| never give your car to
| explaininjs wrote:
| In the military, the folks tasked with Mechanical maintenance
| of vehicles are an entirely different branch with different
| training, infra, etc than those tasked with Electrical
| maintenance of vehicles. Perhaps we need a similar dichotomy on
| the civilian side.
| alexchantavy wrote:
| I saw this on the Gears and Gasoline Youtube channel:
| https://youtu.be/XgOowUWbCdk?t=628 -- looks like a lot of work
| to trace a parasitic drain.
| jeron wrote:
| If you like watching amateur YouTubers rip out their hair
| chasing electrical problems, I recommend checking out
| Tavarish and Samcrac. It turns out cheap flooded auction cars
| have tons of those
| toxik wrote:
| Pine Hollow Auto Diagnostics
|
| South Main Auto
|
| Watch Wes Work
|
| musty1
| millzlane wrote:
| +1 for SMA. The man clearly takes you through the
| troubleshooting process and his train of though.
| legitimayzer wrote:
| > It seems like mechanics really don't like digging into the
| electrical part of the car.
|
| this is like saying that computer programmers don't like
| digging into the proprietary and binary blobs from other
| vendors.
|
| I am trying to say it's not fair to blame mechanics because
| even if they want to dig into the electronics, the car
| manufacturers take active measures to prevent 'random
| mechanics' from digging around.
|
| I suppose there are many rational and reasonable way to justify
| why this is so; probably all having some form of "because
| safety" and "because IP of vendors".
| bonestamp2 wrote:
| > The second told me it's normal for the battery to die if you
| don't drive it for 3 days
|
| No, this is not normal. When the cars are manufactured, they
| often sit for more than 3 days just to get on a train for
| delivery. During transport they often sit for more than 3 days.
| scrlk wrote:
| > It seems like mechanics really don't like digging into the
| electrical part of the car
|
| Probably worth taking it to an auto electrician, rather than a
| mechanic.
| markdoubleyou wrote:
| My last car, a 2007 Acura TSX, had the same problem--it
| wouldn't start after 4 or 5 days (maybe 2 or 3 during the
| winter). This model was from the first wave of touchscreens and
| bluetooth. Mechanics shrugged, pointed to the tiny,
| underpowered battery, and told me to drive it more.
|
| Thankfully there are a lot of car enthusiast forums out there
| that have been plugging away on vBulletin for years. Someone on
| an Acura forum had figured out that the bluetooth module was
| always on and looking for a connection. I tried disconnecting
| it, and the problem was fixed.
| timlin wrote:
| Same problem and same fix for my 2009 Acura MDX.
| fxtentacle wrote:
| Wow. My German car handles being parked for 3 months just fine.
| rootusrootus wrote:
| So does my American car.
| EricE wrote:
| And all three of my Japanese cars too. Definitely not
| normal behavior.
| darrenkopp wrote:
| have similar issue with 2011 nissan maxima w/ key fob. guess i
| have a new weekend project on my hands.
| kccqzy wrote:
| > it's normal for the battery to die if you don't drive it for
| 3 days
|
| I've heard this nonsense a couple times now. I was incredulous
| at first but everyone seems to say this. What are anyone's
| suggestions for a weekend-only car? (I bike to work so I don't
| need a car on weekdays.) Trickle charge the car battery on
| weekdays?
| kybernetyk wrote:
| There's battery kill switches you can install onto the
| battery pole to effectively disconnect everything from the
| battery. This should work for older cars. For newer ones you
| may experience hiccups like reverse camera not working for a
| few hours until it has re-paired itself with the head unit.
| SoftTalker wrote:
| Also the engine and transmission computers may go into
| "learn" mode if they are cold-starting having had no power
| for a while, and so you may have stuff like a wandering
| idle speed for a little while.
| illumin8 wrote:
| This really wouldn't work for any car made in the last 20
| years. Most of them have anti-theft systems that require
| you to put in a PIN to use your stereo if it ever gets
| disconnected from the battery. I suppose you could type
| that in every single time, but there are other computers
| like your automatic transmission management that learn how
| you drive, etc, and might not like to get reset every day.
| windowsrookie wrote:
| This is false. I have owned many different cars from the
| last 20 years and none of them did this when you
| disconnected the battery. A quick google search shows
| that it's Hondas that do this, not "any car made in the
| last 20 years".
| tecleandor wrote:
| Really nonsense. It's true it might be more common due to all
| the additional modules and computers cars have now. If one
| goes crazy, it might drain your battery. But this is only in
| case of a failure. Edit: cold weather can accelerate that.
|
| If it's 'weekend only', battery should be no problem. If
| sometimes you leave it a couple months unused, that might be
| a problem.
|
| Depending on how ready you would like to be when you're going
| to use it, or the access you have to your car (is it far away
| or in your garage?) you could add a connector for a battery
| charger/maintainer (some of them have accessories for plugs
| you can leave permanently, see the NOCO GC002 for an
| example), and/or add a battery switch to easily disconnect
| the battery.
|
| Warning: your radio might ask for a security code if it loses
| battery connectivity. Be sure you have it.
| red-iron-pine wrote:
| > Edit: cold weather can accelerate that.
|
| My Honda HRV dies anytime it gets below -7C. Outside,
| inside, driven a bunch a day or two before -- once it's
| cold that battery taps out.
|
| Probably a vampire drain but I suspect it's just a small
| battery. My old 2013 Mazda 3 starts in -25C without fail.
| Scoundreller wrote:
| Could be a weak starter (and or the combination of that,
| a weak battery and maybe even bad ground straps).
| ghaff wrote:
| I don't have extensive experience with my current car
| bought last summer but 2 weeks in warmer weather definitely
| wasn't an issue.
|
| I agree colder weather is always a bigger issue and at 1-2
| months I'd definitely be thinking of a trickle charger if
| at all possible. An older car I didn't drive in the winter
| would definitely end up with a dead battery if I didn't
| keep it on a charger.
| EricE wrote:
| AGM batteries are a lot more durable than regular lead-
| acid. They can cost a bit more but for me the longer
| life, more resistances to issues if you do run them all
| the way down and their sealed, maintenance free nature
| makes them the first thing I swap out. Optima used to be
| the only commonly available batteries but Costco, for
| example, has AGM equivalents for just about every battery
| out there - you may have to order it and wait a few
| weeks.
|
| They were also the original batteries used in Miata's
| since they give off a lot less hydrogen when charging.
| Since the Miata battery is in the trunk, and all lead
| acid batteries give off hydrogen when charging, and
| hydrogen in an enclosed space can also be rightfully
| called a bomb, having less of that is a good thing!
| johncalvinyoung wrote:
| I must have had a bad run of big H8 AGMs in my Jag and
| Volvo. I think I've replaced about one a year on average.
| The Jag is very subject to parasitic drain and sometimes
| it just didn't come back from running itself out.
|
| Did the Miata not come with a hole in the trunk floor for
| an exhaust hose for the battery? Both of my cars did...
| stocknoob wrote:
| Or disconnect the battery (you'll have to reset the clock,
| etc., which is annoying).
| ChuckNorris89 wrote:
| Not great advice.
|
| Most new-ish cars also store the dinamic engine calibration
| data in ECU RAM so if you disconnect the battery you can
| find your engine running harsher next time. So are the
| values of the headlights auto leveling system and other
| stuff.
|
| You're also risking to reset the radio/media unit security
| code (on cars that aren't too new but also not super old),
| which if you got the car second hand and the former owner
| didn't save the piece of paper it came with and give it to
| you, tough luck unlocking it.
| stocknoob wrote:
| Not ideal to cut power to the entire car, but that
| happens anyway on every battery swap, no?
|
| If you want to get fancy you can isolate the exact fuse
| and switch just that:
|
| https://www.ebay.com/itm/175668177479
|
| Thinking more, given how common parasitic drains are,
| carmakers should have all non-essential fuses in a
| separate subpanel section that can be easily switched
| off/diagnosed.
| pvaldes wrote:
| There are systems that can be attached to save the
| parameters from the car before you disconnect the battery
| or even to provide electricity to the car while the
| battery is being checked in another room. Not common to
| find and most people don't need them, but they exist.
| rconti wrote:
| I try to keep my cars on trickle chargers (Noco Genius 5 in
| my case) when not driven regularly, because regularly killing
| $300 AGM batteries gets expensive.
|
| That said, I'd expect most cars should be able to manage,
| say, 2-3 months. It's when I exceed 4 months with some
| regularity that battery life starts getting sketchy.
|
| If you're driving the car every weekend, I'd expect that
| should be plenty. Note that fancier cars with more electronic
| features don't do well when only driven short distances. If
| you only drive 2-3 miles at a time, you might be discharging
| the battery faster than you're charging it.
| peteradio wrote:
| It's nonsense! If a car is dying after not being driven for
| several months, ok fair enough. If after several days a
| particular year make model dies it deserves a recall!
| FartyMcFarter wrote:
| I didn't drive my 2019 Mercedes for months during the
| pandemic and the battery was fine. It did give me a warning
| when I restarted driving it (I guess the battery was starting
| to get low-ish), but it immediately fixed itself.
| heleninboodler wrote:
| Yeah, if a mechanic told me having the battery die in 3 days
| was normal, I'd stop going to that mechanic.
| chrisdhoover wrote:
| All those cars at long term parking that wont start!
| arscan wrote:
| I did that for the exact same problem on the same model car
| earlier this year, but gave up after trying a few places
| that all said the same thing (including the dealer). Glad
| to see this post though... now I know I'm not the crazy
| one.
| bityard wrote:
| I would expect a _good_ car (no maintenance issues, new
| gas, newer battery) to go at least a couple months
| without being driven and not have any issues upon
| starting it up.
|
| The average car in average condition should go around a
| month without being driven. Anything less than that
| either means a battery nearing the end of its life, not
| getting charged, or a parasitic draw somewhere.
| illumin8 wrote:
| We have a 10 year old Honda Odyssey that we keep just for
| long road trips and it has gone 3-4 months without being
| driven with no issues. I usually do try to fire it up
| every 1-2 months just to make sure the battery gets a
| charge and to avoid long term storage issues around oil
| and belts and other parts that degrade.
| elzbardico wrote:
| I would also make sure to use a fuel stabilizer like
| Pri-G, gasoline in a gas tank, depending on your climate
| can degrade pretty fast.
| maccard wrote:
| No car I've owned in the last decade has actually drained in
| a few days. Any car that does has a problem.
| jsight wrote:
| I have this problem, but it really only becomes an issue
| when a few days becomes a few weeks. Do that a few times
| and the battery will lose capacity too.
| maccard wrote:
| Weeks, sure. 2 weeks is probably on the lower end of
| acceptable though. My car is often left for 2 weeks and
| is completely fine, but most of the time it's weekly.
| jsight wrote:
| Yes, they make battery tenders that are specifically for
| this. They'll trickle charge when needed, but also not charge
| at all when the battery is at the right voltage.
| chrisdhal wrote:
| My wife drives about once a week, probably less on average.
| She has a 2013 Honda CR-V, only 15,000 miles on it. We live
| in Minnesota, so have cold temps, but the car in a garage.
| The car always starts. We've replaced the battery once just
| due to longevity.
|
| Every 3 days? No way.
| yurishimo wrote:
| 15k miles on a 2013 CR-V? Enjoy the last car you'll ever
| own! I assume you know this, but some of the maintenance
| items for that car are 8 years I think; worth checking the
| manual to find out!
| rconti wrote:
| Tires should be first on the list!
| tadfisher wrote:
| You can drive a car from the 90s before they started shipping
| alarms and keyfobs in every vehicle. My 1995 Miata draws just
| enough power to maintain the clock in the radio, and it
| starts just fine after sitting for 6 months (it's not a
| winter car).
| olyjohn wrote:
| My 2000 Ford Explorer has all kinds of electronics and
| modules from the factory. And even my crap I added in... I
| leave my Qi charger, ham radio, Bluetooth FM transmitter
| all running and plugged in, and I can come out a week later
| and the battery is still not dead. And when I'm camping I
| run a 12v van all night long. Truck starts right up every
| time. I don't get what would be draining more power than
| that in a more modern car. You'd think they'd be more
| efficient at not wasting juice.
| KMnO4 wrote:
| You should see if there are carshare options around you.
|
| Even if you're spending $50/weekend (which is a fair amount
| of driving -- Communauto is as low as $3/hr), that's still
| quite a bit cheaper than owning a depreciating asset with
| lifetime maintenance costs (not to even mention insurance and
| fuel).
| ambicapter wrote:
| "You will own nothing and you will be happy"
| tsgagnon wrote:
| This must be the new astroturfing attack against concepts
| like public transportation. I've seen this phrase pop up
| too frequently at this point for it to be organic.
| EricE wrote:
| The simple may see it as astroturfing, others see it as
| an observation by those paying attention. I'm now living
| in a house I own without a mortgage because 20 years ago
| I bought a house and didn't rent. Utilities and property
| taxes are my only expenses. Yes, there is maintenance but
| if you don't think that's also factored into rent you are
| beyond delusional. Landlords aren't going to lose money
| out of the goodness of their hearts. I haven't had a car
| payment in over a decade because I take care of my stuff.
| The car goes in the garage; I don't fill my garage with a
| bunch of useless stuff I will likely never touch again
| (or pay someone else to store it!). Common sense stuff
| like the above, sadly, isn't common sense any more - so
| hence pithy phrases like own nothing and like it. A
| modern day emperor has no clothes, if you will.
| ambicapter wrote:
| Maybe a lot of people just read the news? It was said by
| the leader of the World Economic Forum.
| ambicapter wrote:
| Also, car-sharing is not public transportation? Weird
| comment.
| ryukafalz wrote:
| Oh do I wish there were carshare options near me. Just
| moved from Philadelphia where ZipCar seems to be the only
| remaining contender, and you're lucky if there's one within
| a half hour's walk in the part of the city I was in. It's
| even worse in the town I moved to. There used to be a few
| at the nearby train station, but those seem to have
| disappeared. (This reminds me, I should go cancel my
| membership.)
|
| I'm jealous of the carshare options that seem to be
| available elsewhere. If it were as easy here as in this NJB
| video, it'd be a no-brainer: https://youtu.be/OObwqreAJ48
| Dave_Rosenthal wrote:
| I think a cheap thermal camera would be very helpful in these
| situations with a relatively fast drain. A car battery is ~1
| kWh so anything that drains it in a few days is dissipating on
| the order of 10 watts. In my experience that's very easy to see
| in a thermal camera. Just leave the car in a nice thermally-
| stable place for a day and then go hunting.
| jerrysievert wrote:
| 3 days is definitely not good for an NC. That said, mine is
| usually around 2 months before the battery is drained. That
| should give you some better expectations.
| sterwill wrote:
| 2006 NC owner here with a reasonably new battery. I keep it
| parked in an attached garage, so no extreme cold or heat.
| Mine will always start after leaving it for 1 month. I
| probably left it for 2 months at some point in the last two
| years, and it started, but that feels like pushing it.
|
| The next time a mechanic tells you cars can't sit for a few
| days without a battery drain problem, ask how people who park
| at the airport get home after a two-week trip.
| kybernetyk wrote:
| >It seems like mechanics really don't like digging into the
| electrical part of the car.
|
| If you've ever seen a car's complete wiring harness you'll know
| why. It's not only because there's three gazillions of wires -
| they're also heavily insulated with tape that makes it a
| nightmare to access those wires in the first place.
| dylan604 wrote:
| >there's three gazillions of wires
|
| My old math teacher would deduct points for not listing the
| units.
| rzzzt wrote:
| "Number of wires" is a unitless quantity.
| cloudripper wrote:
| My former English teacher would question why the age of
| your math teacher is relevant in this post.
| toast0 wrote:
| Who said anything about the age of their _old math_
| teacher? You 've got to learn old math and new math,
| presumably with different teachers.
| dylan604 wrote:
| why are you being ageist? I have a new math teacher,
| therefore my previous teacher is my old math teacher.
| airstrike wrote:
| Numbers of wires
| mikrotikker wrote:
| As a practicing brochanic angry pixie spaghetti is the worst
| thing to deal with.
|
| But I've heard so many stories of friends paying hundreds to
| auto sparkies only for the problem to remain.
| peteradio wrote:
| Mechanics are like doctors: find a good one and be grateful.
| rozap wrote:
| It's fairly straightforward if the car is unmodified, as
| everything should be fused. Multi-meter between positive
| terminal and positive lead and pulling each fuse to see when
| the drop goes away will isolate the circuit. Then you've
| narrowed it down pretty far and can go from there.
|
| The horrible thing is if the car is modified, and you discover
| an un-fused circuit.
| everybodyknows wrote:
| > Ammeter across the battery terminals and pulling each fuse
| to see when the drop goes away
|
| How does this compare with the way presented in the article
| based on measuring resistive voltage drop across each fuse in
| turn?
| ilyt wrote:
| Same idea really, just that you have to bother
| disconnecting something and try one by one vs just
| measuring it fuse by fuse.
|
| Other method is getting DC clamp meter with low range (say
| 2A). Then just clamp in on wires. Bit fiddly as they work
| on magnetic field so they need to be reset before measure
| (And can work as compass in a pinch...)
| rzzzt wrote:
| Ye olde ammeters were secretly voltmeters with a low-value
| but high-precision shunt resistor in series with the
| circuit to be measured.
|
| Current passing through the resistor causes a tiny voltage
| drop, which is measured by the meter. As the voltage is
| proportional to the current, the scale painted on the
| cardboard behind the needle did the actual conversion.
|
| In the author's setup the fuse takes the shunt's place; its
| resistance is apparently a known value that can be gathered
| from a datasheet.
| LgWoodenBadger wrote:
| Or you could measure the resistance of the fuse directly
| using a multimeter...
| [deleted]
| ilyt wrote:
| > Ye olde ammeters were secretly voltmeters with a low-
| value but high-precision shunt resistor in series with
| the circuit to be measured.
|
| "ye olde"? That's how every typical one works, till you
| go to clamp meter
|
| > its resistance is apparently a known value that can be
| gathered from a datasheet.
|
| that's... optimistic
| mlyle wrote:
| > Ammeter across the battery terminals
|
| I know what you're trying to say... but this reads like very
| dangerous advice and you may want to revise.
|
| Ammeter between a battery's terminal and the car's electrical
| system.
|
| Also note that you'll probably create sparking when doing
| this, and if the battery has recently been charging this can
| be dangerous (hydrogen outgassing).
| johnwalkr wrote:
| I think the mistake may have actually been writing ammeter
| instead of voltmeter. Ammeter is not safe as general advice
| as a typical one won't be anywhere near large enough
| capacity for working with a car battery and should come
| with a lot of disclaimers about how to hook it up.
| Measuring voltage drop would work but only for fairly high
| loads.
| mlyle wrote:
| > Measuring voltage drop would work but only for fairly
| high loads.
|
| Yah, that doesn't really make sense for small parasitic
| loads.
|
| > Ammeter is not safe as general advice as a typical one
| won't be anywhere near large enough capacity for working
| with a car battery
|
| It should be fine with the car not "on", but the general
| level of danger of doing anything near a car battery
| requires caution.
| duskwuff wrote:
| > Yah, that doesn't really make sense for small parasitic
| loads.
|
| If your multimeter has a sub-mV range -- which a decent
| meter should -- you can measure a voltage drop across the
| battery ground lead. I've successfully done that to
| diagnose a battery draw in my car.
| peteradio wrote:
| Exactly, you are measuring a change, so its the precision
| of the meter not the absolute V. Maybe easier to measure
| on a nearly dead battery?
| duskwuff wrote:
| I'm not talking about measuring the terminal voltage of
| the battery. What I mean is using the ground lead as a
| current shunt by connecting one meter lead to the
| negative battery terminal and the other to where the
| ground lead connects to the vehicle chassis. The voltage
| measured across that shunt is proportional to the amount
| of current being drawn from the battery.
|
| It's the same principle as measuring the voltage across a
| fuse, except it ends up measuring the draw for the whole
| car, not just one circuit.
| pwg wrote:
| > It should be fine with the car not "on"
|
| No. Not if the meter is in "Ammeter" mode (or is purely
| an ammeter only). An ammeter presents a very low
| resistance to the circuit you are attaching it to, low
| enough that for almost all circuits, it is effectively a
| "short".
|
| If one connects an ammeter across a low resistance
| voltage source (i.e., across the car battery) the ammeter
| will appear as a short circuit to the battery, and one or
| more bad things will happen. The 'least bad' will be
| blowing a rather expensive fuse in the ammeter that
| protects it from this kind of accidental use. Several of
| the "most bad" will involve hot molten metal and/or
| extreme heat.
| mlyle wrote:
| > If one connects an ammeter across a low resistance
| voltage source (i.e., across the car battery) the ammeter
| will appear as a short circuit to the battery
|
| Yes. My first comment on this thread says _not to do
| that_ , and suggesting an alternative is "Ammeter between
| a battery's terminal and the car's electrical system."
| instead. https://news.ycombinator.com/item?id=35514652
|
| I was replying to "anywhere near large enough capacity"
| in the next post. The typical 10A range is massive
| overkill for typical parasitic loads in a car, and even
| things like the fuel pump deciding to kick on and run in
| most cars.
| johnwalkr wrote:
| Using an ammeter as you describe would work fine, but the
| topics this thread including mine should come with a
| footnote[1] at least. Especially when this thread shows a
| simple mistake can cause a lot of confusion about what to
| do. My thought process with my comment about capacity was
| that muscle memory makes it likely you'll eventually
| start the car if you're touching the ignition
| switch/button during troubleshooting, although on further
| thought and reading the other comments I'd do the
| following: pull the starter fuse, then use a 10A ammeter
| function of a common multimeter, connected inline between
| the negative harness and the negative terminal and not on
| the positive side.[1]
|
| [1]This is just what I would do. Only do this based on a
| reputable guide if you don't have experience working
| around car batteries.
| rozap wrote:
| heh true, edited post to maybe save someone some sparks.
| sokoloff wrote:
| I've had unknown draws before and many times they're not
| constant draws. A constant draw is easy and quick to find. A
| draw that only happens when some module or other wakes up is
| a lot harder to find.
| flibbityflob wrote:
| As an example, my 2017 Corolla runs the fuel pump for a
| while _5 hours after shutdown_ to test fuel system
| pressurization. I didn't even know until I recently started
| parking it inside and I finally heard it running.
| rootusrootus wrote:
| Yeah that's pretty normal across different manufacturers,
| and you only hear it if you park in a quiet garage and
| happen to be in the garage at the moment it turns on to
| do it's thing. It's testing the seal of the fuel cap to
| make sure you aren't just venting gasoline fumes.
| Scoundreller wrote:
| And usually it only runs in a certain temperature range.
| Winter climate cars may get several months between a
| test.
| officeplant wrote:
| I learned about this with my 2013 Scion iQ. I was living
| with my brother who didn't allow weed smoking in or near
| the house so I would go hotbox my car.
|
| Weirded me out the first time I'm sitting there in
| silence smoking a bowl and suddenly fuel pump noises.
| Which were easier than normal to hear because I took the
| back seats (the only sound deadening in the back) out of
| that car so I'd have room for a full size spare tire
| instead.
|
| With my current car (2020 Kia Sportage) I've noticed the
| head unit is waking up before I even start the car. As
| soon as you unlock the car I can see my flash drive light
| up with activity as the head unit gets ready to pickup
| music from where it left off.
| gdavisson wrote:
| I recently watched a YouTube video from someone who'd
| tracked a nasty intermittent parasitic draw [0]. The
| problem only happened after turning the ignition on & back
| off (so the standard test of disconnecting the battery &
| reconnecting via the ammeter wouldn't show it), and the
| draw cycled between 3.6A and 0.3A.
|
| Also, after turning the ignition on & back off there were a
| lot of (normal) transient draws (from things like the dome
| light that don't turn off immediately). Even with the
| problem circuit disconnected, it drew around 6A (!)
| immediately after the ignition was switched off, dropped to
| 0.4A after about a minute, and sat at that level for
| another 9 minutes before dropping again to 0.06A. That
| means if he hadn't waited ~10 minutes _per test_ , he'd
| have been chasing draws that were actually normal.
|
| Combine an intermittent fault with intermittent normal
| behavior, and you've got a troubleshooting nightmare.
|
| [0] https://www.youtube.com/watch?v=rVScppKsfHs
| falcolas wrote:
| Yes. I had a Dodge Charger where the parasitic draw
| wouldn't really become problematic until 3 days after you
| re-attached the battery. At which point it would be so bad
| it would discharge from full to empty overnight. It could
| even out-draw a trickle charger.
|
| I took it to several mechanics who couldn't find anything -
| because they'd unplug the battery to add a meter into the
| circuit. They weren't willing to wait 3 days afterwards to
| come back to it.
|
| I ended up disconnecting the battery overnight. Worked fine
| then. Traded it in; I feel a bit bad for the next buyer.
| voldacar wrote:
| Ammeter in series, not across the terminals! Unless you are
| trying to weld something :]
| AlexandrB wrote:
| Realistically, you'll just pop the fuse in the ammeter. If
| it's a nice ammeter the fuse might be pretty expensive.
| oliwarner wrote:
| > mechanics really don't like digging into the electrical
|
| Mechanics don't like fishing expeditions for nonessential
| things. $100/h for 2+ hours diagnostic, followed by tedious
| parts to replace and pair up.
|
| A new battery every couple of years and a trickle charger
| probably seems like better value to them.
| jseutter wrote:
| Eric O from the South Main Auto youtube channel has some great
| videos on tracking down parasitic drains on modern-ish cars.
| From his videos I learned that often cars won't fully sleep for
| up to 45 minutes depending on the model and manufacturer, as
| well as checking for the voltage drop across fuses to figure
| out which circuit is draining the battery. With this I was able
| to track down a parasitic drain in my 2000 Beetle (failing door
| lock). I'm sure he mentioned other tips as well but those are
| the ones that stick out to me.
| everybodyknows wrote:
| Anecdata: Some Hondas (e.g . 2010 Element) exert enough parasitic
| drain to put the car into a chronically undercharged state if a
| door is left ajar overnight.
|
| The wrong thinking turned out to be: Car is safe in garage,
| interior lights go off, and my hands are full now -- why bother
| going back to the door to shut it completely?
| karolist wrote:
| My father (a professional auto mechanic) took about 6 months to
| find a random engine shutoff during harder cornering in his
| Toyota, the culprit was a damaged inner insulation layer for a
| few wires within the wrapped wiring harness for the ECU, engine
| moving on the engine mounts would sometimes cause a slight
| harness shift and a short would cause a hard reset of the ECU.
|
| Another story I have is my computer geek friend finding an issue
| with my Subaru Legacy, when no other mechanic could (I tried 3).
| The issue was that the car was old, first gen OBD, he downloaded
| some legacy asm ECU reader and made a diagnostic cable from spare
| parts, the issue was that the car would not start when cold, or
| be extremely hard to start. The culprit was damaged wire that
| tells the ECU that the engine is in cranking condition, therefore
| needs a different fuelling mode, without seeing this mode there
| was not enough fuel to start when cranking. Eventually this was
| found by hooking up an oscillograph to see the injector impulse
| length (duty cycle), as the old gen. diagnostic didn't show any
| errors, he compared a working car injectors to mine when cranking
| cold and found this. 10 years later I'm still amazed by his skill
| and dedication, I'd have scrapped the car otherwise. The car was
| sold eventually to another person who restored it (rust repair
| mostly) and his wife still drives it to this day, a 1994 Subaru
| Legacy.
| Spare_account wrote:
| This methodical approach to vehicle diagnostics is something
| you can see on YouTube at South Main Auto Repair
|
| https://www.youtube.com/@SouthMainAuto
|
| Eric regularly takes the viewer through the entire process
| including sometimes measuring electronic components with
| diagnostic tools that include oscilloscope functions.
| PuffinBlue wrote:
| Pine Hollow Auto Diagnostics goes even deeper. And focuses
| much more on the diagnostic. These two channels are good
| together in that they show different sides of the auto repair
| industry.
|
| Ivan has done some parasitic drain diagnosis in the last few
| videos, including a new custom made logger that he had sent
| to him for tracking drain over long duration (like overnight
| or a couple days).
|
| If you like South Main Auto and you havent' seen Pone Hollow
| Auto Diagnistics, I think you'll like it.
|
| https://www.youtube.com/c/PineHollowAutoDiagnostics
| ryandrake wrote:
| Your friend's fuel issue seems a lot like the intermittent no-
| start, low fuel pressure issue I have been debugging (3-series)
| for over a year now. It has defeated three dealerships and two
| independent mechanics so far, so I'm taking over the diagnosis
| now. No clue yet but today's cars have too damn many computers
| in them.
| karolist wrote:
| which engine is that? I had an N54 335 for 5 years too, even
| E36 era BMWs have vastly superior error logging compared to
| JDM from that vintage. I hope you find your issue, but if it
| defeated dealerships it sounds troublesome. Log some live
| data with INPA if it's an older one, I have no experience
| with BMWs post EXX series to drop any advice...
| ryandrake wrote:
| Yea, N54. INPA helps confirm things, but just the idea that
| you have to pour over logs to diagnose a system that should
| be simple and straightforward... sigh. My last car was from
| the '80s and you could wrench pretty much anything you
| needed to without having to negotiate with a dozen
| computers running the show.
| karolist wrote:
| I loved my N54 dearly, HPFP is a consumable item there
| though (30-50k miles), I'd change that as a precaution,
| especially if your car is tuned.
| Spare_account wrote:
| Take a look at my other comment
|
| https://news.ycombinator.com/item?id=35516985
| aftbit wrote:
| I have a parasitic draw on my 2004 Honda Civic back in college.
| All the mechanics I went to wanted to sell me a battery or
| alternator. I finally bought a meter with a 10A current limit and
| tested every fuse each time I parked. It turned out to be an
| issue with the magnetic AC clutch, so I drove it for 2 more years
| with the fuse for that component removed.
| bonestamp2 wrote:
| In hindsight, you could have put a relay on that circuit that
| was powered by some other circuit... so it only connected the
| AC clutch circuit when the vehicle was on.
| 1970-01-01 wrote:
| Intermittent car issues are the worst! Related is the 'My car
| hates vanilla ice cream' story:
|
| https://web.archive.org/web/20060213052358/http://www.campbe...
| netsharc wrote:
| Maybe I've read this before, but I guessed by the problem
| description that the answer probably had something to do with
| time...
| teddyh wrote:
| That's an old urban legend: https://www.snopes.com/fact-
| check/cone-of-silence/
| Baeocystin wrote:
| Harbor Freight sells a $15 cheapie solar panel (with diode) that
| plugs straight in to a car's cigarette lighter that essentially
| 'solves' most parasitic drain problems, if you park outdoors, at
| least.
|
| https://www.harborfreight.com/15-watt-solar-battery-maintain...
|
| (Not all cars have ports that are live with the key off, but the
| panel has other ways to wire it)
| benatkin wrote:
| He should move to San Jose.
| bityard wrote:
| One thing I haven't seen mentioned yet: If your battery is dying
| way sooner than it should be, and if you have _any_ aftermarket
| equipment installed (radio, backup cam, alarm, remote start,
| trailer light module), that should always be the VERY first thing
| to suspect.
|
| These things are not engineered to the same requirements as the
| OEM electronics, and if they are drawing 10s of milliamps while
| the car is off, that is certainly enough that you wouldn't notice
| an issue with a newer batter and a car being driven every day.
| But if your driving patterns change and the battery gets older,
| suddenly your battery is dying all the time and "nothing has
| changed."
| anodyne33 wrote:
| tl;dr my dealer had my car for a week to diagnose an intermittent
| electrical gremlin.
|
| My maddening intermittent electrical gremlin was with my new to
| me Mazda3. Occasionally and randomly after in the first few
| months I had it the throttle would "go to sleep" during normal
| driving. By that I mean in the process of normal driving I'd
| suddenly have no throttle response, the car would go to idle, and
| the only way to get it back was to completely get off the gas
| pedal and it would respond again as usual. I'm appreciative that
| worked, but I couldn't shake the idea that if that were to happen
| during hard acceleration bad things could happen.
|
| My first trip to the dealer yielded a recording in the event log
| of the throttle shutting off because it saw throttle and brake at
| the same time, an expected behavior I was told. I assured the
| mechanic and service manager that I was almost certain this
| wasn't the case, they had no other explanation, I continued to
| have the problem and made certain when it happened that I hadn't
| somehow been on both pedals.
|
| After an email to Mazda's support line with some technical
| details hoping to get my situation into the right hands, I got a
| call from the dealer asking to hang onto it until they could
| replicate the problem.
|
| The service manager or someone else in the shop drove it for the
| better part of a week, taking real time telemetry while they were
| in it while I was in a loaner.
|
| Turned out that the problem was the second brake switch hanging
| on. I found out that there's one switch that talks too the ECU
| and another that talks to the brake lights, the former being the
| culprit.
|
| Frustrating as could be, but like a good nerd I found the final
| diagnosis fascinating. I also wonder and would like to believe
| that my detailed and informed email to the mother ship made
| someone pass it up the line until it got into the right hands.
| nuancebydefault wrote:
| Once you find the fuse that passes the highest current, why not
| just place a switch button in series with it? Turn it off when
| exiting the car. Add an LED to show when it is on.
| Scoundreller wrote:
| If you're going to do all that, just rewire it so the circuit
| only turns on with key-on.
| falcolas wrote:
| Personally, I'd go for a relay on a non-problematic circuit.
|
| But I also get why you might just leave it disconnected - if
| it's pulling a few more amps with no clear cause, what is going
| to go wrong with it next, and what vital system will it take
| with it?
| nuancebydefault wrote:
| Oh a relay that goes on after you turned the key would be
| very handy. It is rather easy to find a point where there's
| only a voltage present after/while starting.
|
| Of course, when the array controlled circuit would be vital
| for entering or starting, this would not be an option.
| frankus wrote:
| A recent HN post mentioned that a signal like radar from a nearby
| airport can sometimes be enough to kick the keyless sensor module
| out of sleep mode and drain the battery. (This was the one about
| CAN injection attacks).
| IshKebab wrote:
| > Since I don't have Mazda's proprieratry M-MDS diagnostic tool,
| I couldn't disable the keyless module in software myself.
|
| Ugh, imagine if normal computers were like that. "Since I don't
| have Intel's proprietary I-DBT diagnostic tool, I couldn't
| disable the wifi in software myself."
|
| I guess we're half way there with phones.
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