Can't Find Battery Drain
 

Hey all, first time poster here. I bought a 2003 R50 with HK sound system last summer and late in the year I noticed that I have some battery drain going on - driving every day it usually is fine, but if I leave it more than 2-3, it's dead. I store it for the winter and finally got around to trying to diagnose it, but have hit a wall.

Full disclosure, I'm relatively new to electrical work, so I could absolutely be doing something wrong

I threw a multimeter on the battery, and saw that it was pulling anywhere from 1.3 to 1.6 amps while the vehicle was fully shutdown. Everything I read says that it should be sub .5 amps, which explains the drawdown.

The weird part is, I then started to pull fuses (both the ones inside the engine compartment and inside the driver side - US - door) and check the amps, and none of the fuses made any difference. So I'm at a loss.

Possibly related note due to reading about how bad the HK sound systems are - my amplifier went out late last summer, and I disconnected it completely as I haven't gotten around to replacing the sound system. I wouldn't think that disconnecting the bad amplifier would cause battery drain, but I have a small suspicion that the battery draw might somehow be related to the sound system in general. Or I could be completely wrong

Any ideas?

0.5 A when asleep is massive. You should probably be sub 50 mA, but I’ve never checked to see what the BMW spec is when all the modules are asleep. One thing that springs to mind is the high current fuses on the back of the underhood fuse panel. There are also a couple of relays on the back of the interior panel, IIRC.

Another thing to check is for a leaky diode in the alternator. Disconnect the B+ cable from it and see if your amps drop. It's probably easier to do this at the jumper terminal by the air filter rather than trying to access the back side of the alternator.

Thanks for the reply, to get to the relays on the back of the interior panel it appears I have to remove some trim pieces? Or is there a different way to access?

I’ve never had that side apart before, actually, but I wouldn’t be surprised if removing trim is necessary.

So I pulled the 2 additional relays (I think there’s just those that I was missing) on the interior panel and that did nothing. I also disconnected the cable that’s bolted onto the positive terminal connection and that drops the drain about .3 amps (from 1.6 to 1.3). I believe that’s connected to the fuse box battery connection (which you can see in the picture) because disconnecting that side does the same thing and when they are both disconnected there’s no change.

Assuming what I disconnected is not the alternator wire but the fuse box, I can’t seem to find a wire that’s semi easy to access near the battery/air filter. Does anyone have a diagram/visual for this?

https://cimg9.ibsrv.net/gimg/www.nor...ccd23aa2c.jpeg

Has your car done this the entire time you've had it or did it just start?

When I got my first mini it had a drain. I stumbled onto it looking at something else. There was a GPS tracker hardwired into the car at the OBD2 port. Maybe there's something like that on your car.