Starting issue; something draining the battery? [Archive] - Bimmerforums

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nowbimmin

01-20-2009, 08:25 PM

I went to look at a 94 325is today. At first he was having trouble getting it started; he told me earlier there is something draining the battery, his battery is relatively new.
When he was trying to start it, it was cranking. After some time I left; he called me shortly after and said that it was running; I came back.
It had been running for a good twenty minutes. He stated that he replaced the alternator recently; so I asked him if he would disconnect the battery to be sure that wasn't the problem; he did and it kept running.
He hooked it back up and was curious himself if it would start after it had been shut off. So I shut it off and tried to start it and nothing.
Hooked it back up to the portable battery starting thing (I dunno the technical term) and It fired right up. I took it for a spin and it ran fine.
When I got back I told him to switch batteries with one he knew was charged and he told me that he'd done that already and the battery would be dead the next morning. I didn't see any lights left on in the interior and Checked that the trunk light went off. Also looked at the wiring on the trunk lid and it looked good.
I've done some searching and come down to it possibly being a diode? I don't know anything about this diode though. Anyone care to elaborate?

Thanks all

richbarn2

01-20-2009, 08:50 PM

He may have been talking about the diodes in the alt, but if its new its not likely that is the problem. Several members here have been fighting a similar problem. I have always used an ammeter, but a couple bright members suggested using a test light in series with the ground cable. If its drawing enough to kill the batt, it will light the test light. Start pulling fuses til you find the culprit.

Common killers are the trunk light not switching off, same deal with the glovebox light, depending on how original the wiring is (hacked into for aftermarket stereo, lighting, alarm ect...) it could be simple or you may have to dig deep...

nowbimmin

01-20-2009, 09:07 PM

richbarn2

01-20-2009, 10:10 PM

I did notice a small gauge wire coming off the positive battery terminal. And I know that it has XM radio installed. In a rather crappy way (ran the transmitter through the trunk out the rear window and onto the roof.

You wont know for sure til you use either an ammeter or a testlight to verify the draw...

FWIW, the xm receiver (antenna) will work on the rear deck, it doesnt have to be smacked up on the roof or trunk...

nowbimmin

01-20-2009, 10:13 PM

I sure don't car for it. It's gone if I do get the car. which I think I should; doesn't sound like a major problem.