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I fixed a parasitic drain on my car in 408 days

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

#191

Post by tonyarkles »

JohnFen wrote: post #167
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.…

I wonder if installing a switch to disconnect the car's battery entirely would be an acceptable (but obviously hacky) solution.

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.

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

#192

Post by sixstringtheory »

anamexis wrote: post #170
sixstringtheory wrote: post #152

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…

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.

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.

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

#193

Post by Nifty3929 »

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.…

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

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

#194

Post by ninjanicely »

anamexis wrote: post #170
sixstringtheory wrote: post #152

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…

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.

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.

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

#195

Post by anodyne33 »

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.

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

#196

Post by jxramos »

stuff4ben wrote: post #129
ksherlock wrote: post #60

Earlier quoted context omitted.

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.

That usually doesn't work anymore as mechanics can tell that you've done that when hooking up the ODBII port.

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.

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

#197

Post by LgWoodenBadger »

rzzzt wrote: post #95
everybodyknows wrote: post #31

Earlier quoted context omitted.

> 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…

Or you could measure the resistance of the fuse directly using a multimeter...

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

#198

Post by Spare_account »

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…

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.

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

#199

Post by pvaldes »

KingMachiavelli wrote: post #134

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 act…

> 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).

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

#200

Post by karolist »

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.

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...
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