what can drain the battery over night

Asked by Jun 07, 2015 at 09:32 AM about the 2004 BMW 5 Series 525i

Question type: Maintenance & Repair

battery tested ok ,recharged it
what can i look for

1 Answer

102,115

The best way to find a draw is to put a test in between a battery post and the cable end, positive or negative it doesn't matter, if the lamp turns on you have a draw large enough to kill a battery overnight, then you have to start eliminating circuits, the first thing to do is electrically disconnect the alternator, if the lamp goes out you found your problem, if it doesn't then you need to start pulling fuses one at a time noting where each fuse went until the light goes out, when that happens find out what items are on that fuse and repair or replace the one causing the draw, then start putting it back together making sure the lamp stays off, finally reconnect the alternator. Now a note about parasitic loads, you might notice at first that the lamp will just glow slightly not a bright light, this is normal.

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