1995 BMW M3 Battery keeps dying

FLALLEYCAT

MEMBER
1995 BMW M3

Electrical problem
1995 BMW M3 Engine Size unknown Wheel Drive Type unknown Manual 66,000 miles

Actually, it won't hold a charge at all. AAA tested the battery and said it was still good, jumped it for me. I kept it running for about 45 minutes. It did restart immediately after I shut it off. Next morning, however, dead again. I'm no car person but wonder if perhaps there is something I could check before heading off to the Expensive BMW shop.

Thanks for any suggestions!
Alley

1 Reply

MERLIN2021

MECHANIC
17,250 POSTS

Get an analog ammeter remove the negative battery cable, attach the red lead to the battery post, black lead to cable end, then pull fuses one at a time, make sure there are no accessories or lights in the on position, Key off! Close the door after each fuse and check meter, when you pull the fuse for the bad circuit, the meter will drop to 50 milli amps or so. Check all fuses, even under the hood. If meter does not drop, remove the battery connection from the alternator, if it drops now, the diodes are bad in the alternator. Put the fuse back in were it goes as you go so you don't forget which fuse goes were! What you want is to get the key off draw below 50MA or.05 amp (which BMW considers nominal)