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2002 BMW 530i

Question: BATTERY CONTINUES TO DRAIN FOR UP TO 4 WEEKS and on the Couch till fixed

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davetexas, Arlington, TX, May 28, 2009, 19:25
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Something is so very slowly taking my wifes battery down. Ive rechared the battery and 4 weeks later its down again and wont start. Ive checked the CD player thats not it. The mechanic fixed the fan motor etc thats not it.
What else could this problem be? What can I specifically check with a meter etc to see what is so SLOWLY taking this battery down and me on the couch.

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  • Answer #1

    patrick mannion from Greg Solow's Engine Room, May 28, 2009, 22:12
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    First charge and properly check the battery to ensure it is not the source of the problem, ie a suphated battery that will not hold a charge.
    To check which circuit is running down the battery you need a wiring diagram and an amp meter. By disconnecting the battery and placing an ampmeter in series with the positive battery cable, note the "draw on the battery" (.2 Amps is normal), if you have say 1.8 Amps start disconnecting the fuses one at a time a noting the battery draw. When the battery draw drops (from the example 1.8 Amps) to .2 Amps you have narrowed down which circuit the battery draw is occurring on and can narrow down your tests on those circuits.

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  • Answer #2

    dandd May 29, 2009, 12:47
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    The 5 series BMWs have had problems with an interior light relay sticking on and slowly draining the battery. It is tough to diagnose these because it does not always turn on or leave on the interior lights. Every factory BMW class always brings this up for slow drains, so it is worth checking if the battery and charging system check out as Pat suggests.

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    Visitor, September 30, 2010, 21:11

    That was very helpful thank you. My friends 2002 530i would occasionally have problems with the dome light staying on and the battery draining. That did the trick.

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  • Answer #3

    AlWhit_2002_530i September 27, 2009, 04:01
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    I had a similar problem and I'm sure there amy be a number of causes. For me, it turned out to be a bad resistor in the radiatior cooling fdan curcuit. The cooling fan would not shut off. This drained the battery. My BMW dealer replaced the resistor and no more battery drain.

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  • Answer #4

    kcook320 October 20, 2009, 03:50
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    I had the exact same thing and it was a resistor for the interior fan/blower. Mechanic said it was a common problem. Symptom was is that I could not control the internal blower - it would go fast/slow/fast/slow on it's own. Good luck.

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