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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

#91

Post by Scoundreller »

rootusrootus wrote: post #72
flibbityflob wrote: post #21

Earlier quoted context omitted.

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.

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.

And usually it only runs in a certain temperature range. Winter climate cars may get several months between a test.

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

#92

Post by scrlk »

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

Probably worth taking it to an auto electrician, rather than a mechanic.

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

#93

Post by rozap »

mlyle wrote: post #32
rozap wrote: post #9

Earlier quoted context omitted.

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.

> 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).

heh true, edited post to maybe save someone some sparks.

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

#94

Post by jeron »

alexchantavy wrote: post #88
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…

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.

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

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

#95

Post by rzzzt »

everybodyknows wrote: post #31
rozap wrote: post #9

Earlier quoted context omitted.

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.

> 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?

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.

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

#96

Post by lylejantzi3rd »

cwillu wrote: post #63
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.…

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.

That's a great idea. I can't believe I didn't think of that. Thanks!

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

#97

Post by pwg »

mlyle wrote: post #59
johnwalkr wrote: post #54

Earlier quoted context omitted.

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.

> 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.

> 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.

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

#98

Post by pugworthy »

rootusrootus wrote: post #77
jws wrote: post #2

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.

> 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.

Probably not an issue with more modern systems with solar panels and the detector on the house batteries.

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

#100

Post by officeplant »

flibbityflob wrote: post #21
sokoloff wrote: post #14

Earlier quoted context omitted.

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.

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.

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.

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