I fixed a parasitic drain on my car in 408 days • Hacker News Board

Re: I fixed a parasitic drain on my car in 408 days

#141

Post by bityard » Mon, Apr 10, 2023, 7:09 PM UTC

arscan wrote: post #120

heleninboodler wrote: post #87

Earlier quoted context omitted.

Yeah, if a mechanic told me having the battery die in 3 days was normal, I'd stop going to that mechanic.

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.

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.

Re: I fixed a parasitic drain on my car in 408 days

#142

Post by jerrysievert » Mon, Apr 10, 2023, 7:11 PM UTC

overthrow wrote: post #3

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 myse…

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.

Re: I fixed a parasitic drain on my car in 408 days

#143

Post by fullstop » Mon, Apr 10, 2023, 7:12 PM UTC

blobbers wrote: post #11

Is it possible the key fob just needs replacement and is causing the intermittent sleep failure?

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.

Re: I fixed a parasitic drain on my car in 408 days

#144

Post by jessaustin » Mon, Apr 10, 2023, 7:12 PM UTC

bityard wrote: post #131

jessaustin wrote: post #123

Earlier quoted context omitted.

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...

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…

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...

Re: I fixed a parasitic drain on my car in 408 days

#145

Post by fullstop » Mon, Apr 10, 2023, 7:15 PM UTC

"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.

Re: I fixed a parasitic drain on my car in 408 days

#146

Post by jimmytucson » Mon, Apr 10, 2023, 7:16 PM UTC

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.

Re: I fixed a parasitic drain on my car in 408 days

#147

Post by aidos » Mon, Apr 10, 2023, 7:17 PM UTC

ssharp wrote: post #130

cwillu wrote: post #63

Earlier quoted context omitted.

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.

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 e…

“path of least resistance” is very fitting.

Re: I fixed a parasitic drain on my car in 408 days

#148

Post by legitster » Mon, Apr 10, 2023, 7:18 PM UTC

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.

Re: I fixed a parasitic drain on my car in 408 days

#149

Post by grokx » Mon, Apr 10, 2023, 7:19 PM UTC

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 4200€ 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.

Re: I fixed a parasitic drain on my car in 408 days

#150

Post by sixothree » Mon, Apr 10, 2023, 7:20 PM UTC

lylejantzi3rd wrote: post #28

overthrow wrote: post #3

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 myse…

> 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.…

> 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.