E30 Dead Battery Syndrome

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Brad - 27 Jan 2007 00:16 GMT

My 88 325ix began having a dead battery after sitting a few days.
Thought the old Sears Diehard was finally going bad and bought a new
Interstate Battery. I'm still having the same problem, I've checked the
obvious, trunk and glove box lights not going out. Anyone have a clue as
what else to look for?

Brad,
88 325ix
88 M3

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Dave Plowman (News) - 27 Jan 2007 00:50 GMT

> My 88 325ix began having a dead battery after sitting a few days.
> Thought the old Sears Diehard was finally going bad and bought a new
> Interstate Battery. I'm still having the same problem, I've checked the
> obvious, trunk and glove box lights not going out. Anyone have a clue as
> what else to look for?

A start is to temporally wire in an ammeter (0-10 amps) and check the
quiescent current. Anything over about 0.030 amps (30mA) requires
checking, but if it's going flat in a few days it will be much more than
that. So start on the 1-10 amp range and then use a lower one to get an
accurate reading. If it's very high - more than 1 amp - start pulling out
fuses and see if it goes lower. A reading of several amps might be a
failed alternator diode - easily checked by disconnecting the alternator.
Other possibilities are an aftermarket booster amp on the stereo not
shutting down.

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Dave Plowman dave@davenoise.co.uk London SW
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greg1120@hotmail.com - 29 Jan 2007 15:04 GMT

> My 88 325ix began having a dead battery after sitting a few days.
> Thought the old Sears Diehard was finally going bad and bought a new
[quoted text clipped - 5 lines]
> 88 325ix
> 88 M3

Sounds like you have a parasitic leak somewhere in your electrical
system. My sister had the same problem in her 89 E30 and it turned
out to be a continously running blower motor in her A/C system.

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