Technical Help needed... Power Draining...

[Zoso]

This problem isn't happening to my M3... but it is causing me to have to drive the M3 to work every day so I think that warrants a place here :)

My other car is having electrical problems. A couple of months ago, the (non-BMW) car wouldn't start... even when I tried to jump it, it would finally start after 15 minutes of being hooked up to the other car or not start at all.

While trying to diagnose the problems, I had the car hooked up to another car for 15 minutes and it wouldn't start... even the dome lights were dim... I then disconnected the negative terminal to the battery and the car started right up and kept running. This told me that there was something wrong with the battery and that the alternator was working fine since that car ran fine with the battery disconnected.

So I bought a new battery and installed it and the car worked great from there on....

NOW... a couple of months later the car won't start again.... and it is a power problem. The dome doesn't come on and the electric doors don't work...

I'm guessing that somewhere I have an electrical drain... something must be draining the battery... but I don't know where.

I have an aftermarket stereo in there and an amp... but they have been in the car for many years now. I also went through and checked all the wires on the stereo and everything looked good.

Any suggestions on where to start looking for what is draining the battery?

[BJO]

check your stereo connections. i've had amps that stay on even after the car was turned off.

[UD///M]

I too suspect something with the stereo. Do you have a large power cap in there somewhere? The reason why I ask is that when they get old, the tend to act like a short circuit. In other words their leakage rate goes way up. It will drain the battery.

Try completely disconnecting power to the stereo amp as diagnosis. Run with the car this way for a few days. Let us know what happens.

[Zoso]

the Denon amp I have is low wattage... so I have no power capacitors on it.

I suspect the stereo too... that is why I've checked all the connections and everything looked ok. Perhaps I'll take the amp completely out and see what that does.

If it took a couple of months for this problem to resurface after I bought the new battery, I'm worried that if I remove the amp and recharge the battery it may take a couple more months to determine if there is still a problem.

[Jim O.]

Charge the battery, then with your car turned off, put a multimeter set to amps inline (serial) with the ground wire to check the amount of current that is flowing. Start pulling fuses, watching how much the current reading drops. That way, you should be able to isolate which circuit is pulling the most juice, and you know where to look to fix the problem.

Jim

[98///M-DROPTOP]

I seem to remember a post here o maybe another forum about the OBC and a power drain situation but I can't remember what the fix was. Anyone else remember this or did I just make it up:dunno

[Zoso]

Luckly this problem isn't happening to my M3... it's happening to my winter/commuter/mt.bike & snowboard hauler car

Jim O.... thanks. that is great advice!