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Discussion Starter · #1 ·
We're new to the community and excited to join it and start contributing, although, we'll be asking alot more questions than answering them for now.

We purchased the 1985 325e from a guy this past weekend. He claims he bought the battery this month, although, it's only sat for a few days and the battery is completely dead. We did a parasitic drain test and narrowed it down to FUSE 27 which is your interior lights, heater, automatic locks, horn and audio system.

We are new to BMW's and want to somehow figure out where the drain is happening. What is the best way to locate the drain? So far we know it's coming from FUSE 27. What process should we take to actually locate what is doing it and fix it?
 

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First, welcome to the forum and welcome to working on 30+ year old cars...always an adventure. There is really no easy method to track down drains like you describe, time to start unplugging things. I would start with the trunk light, that could be on and you would never know it.
 

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Discussion Starter · #3 ·
First, welcome to the forum and welcome to working on 30+ year old cars...always an adventure. There is really no easy method to track down drains like you describe, time to start unplugging things. I would start with the trunk light, that could be on and you would never know it.
Hey Tomstin... Appreciate the advice. This weekend we start unplugging. What's odd is that FUSE 27 is for the audio system, although, after unplugging the FUSE, the radio is still on and rear speakers still work. The sub and two front speakers don't work. So half of the system turns off when unplugging FUSE 27. Anyway, we'll start unplugging and go from there. We've been told and have read that this is common in these cars and usually boil down to one thing and thought maybe someone might have had the same issue and could share what they found to be the problem. We'll see.

Thanks again for the reply!
 

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Discussion Starter · #5 · (Edited)
SOLVED: Parasitic Drain on 1985 325e

Well, with FUSE 27 pulled, we went back to testing all the fuses and wires. Locking doors, unplugging lights, etc. Nothing worked.

Just by chance this morning we figured out where the drain was happening. I got fed up and went down the Youtube rabbit hole and searched, "Parasitic drain 1985 325e" and scrolled through quite a few until I came across this video that was 10 seconds long. He said he found the drain in the weirdest spot (isn't to weird). Only 10 seconds...

Showed him drop his phone in the trunk while recording, then he shut the trunk. At first I couldn't figure out what he was doing and what it had to do with the drain. He didn't say anything. And then I saw it... The trunk light stayed on while the trunk was shut.

I thought, NO way, couldn't be that.

So I opened the trunk, hit record on my phone and dropped it in the trunk. Shut the trunk and after 5 seconds, opened up the trunk and watched what I just recorded.

It was like catching a thief in your house, I was looking at the culprit. The trunk light was still on even though the trunk was closed.

I opened the trunk and that's when I saw that the trigger that shuts the light off was broken in half. So when the trunk shuts, it doesn't even come close to pressing in far enough to turn the light off.

I pulled out the light and did a meter test on FUSE 27 and FUSE 21. BOOM, we're at 0. No drain.

I just bought a freakin' new battery for no reason. I have the old one recharging / repairing in the garage. So now I have two ... :(

SO, SOLVED. I feel I just saw bigfoot and didn't have to go through an exhaustive hunt.
 
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