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I fixed a parasitic drain on my car in 408 days

davidmuller.github.io

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

#201

Post by jobead »

Nifty3929 wrote: post #193
lylejantzi3rd wrote: post #28

Earlier quoted context omitted.

> 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.…

What are coded parts? I spent a minute googling and couldn’t come up with anything that seemed right.

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)

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

#202

Post by Spare_account »

ryandrake wrote: post #188
karolist wrote: post #68

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…

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.

Take a look at my other comment

https://news.ycombinator.com/item?id=35516985

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

#203

Post by chrisdhoover »

heleninboodler wrote: post #87
kccqzy wrote: post #7

Earlier quoted context omitted.

> 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?

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

All those cars at long term parking that wont start!

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

#204

Post by JPws_Prntr_Fngr »

legitster wrote: post #160
BoorishBears wrote: post #55

Earlier quoted context omitted.

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)

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.

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)

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

#205

Post by gengkev »

WirelessGigabit wrote: post #173
civilized wrote: post #166

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…

My car beeps loudly and angrily at me if the doors are not 100% closed when I hit the close button on the fob.

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.

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

#206

Post by jseutter »

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…

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.

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

#207

Post by MaKey »

jessaustin wrote: post #144
bityard wrote: post #131

Earlier quoted context omitted.

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...

AFAIK the fuses have contact points you can use to measure the current.

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

#208

Post by johnwalkr »

mlyle wrote: post #105
pwg wrote: post #97

Earlier quoted context omitted.

> 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 batte…

> 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 enoug…

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.

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

#209

Post by buescher »

blobbers wrote: post #11

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

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.
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