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E36 (1991 - 1999)
The E36 chassis 3-Series BMW was a huge hit among driving enthusiasts from the first moment the car hit the pavement. The E36 won numerous awards over the years it was produced and is still a favorite of many BMW enthusiasts to this day! -- View the E36 Wiki

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  #1  
Old 10-06-2014, 05:50 PM
sausalitoroman sausalitoroman is offline
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Location: Sausalito
 
Join Date: Dec 2012
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Mein Auto: 528i
Battery draining

My battery checks out ok but something keeps draining it. Sometimes the battery drains in a matter of minutes and other times over a matter days.


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  #2  
Old 10-07-2014, 10:09 AM
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hornhospital hornhospital is offline
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Mein Auto: 1995 318is / 1993 325is
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Do you have a digital multi meter (DMM)? You can locate the circuit that has the parasitic drain by taking either the ground side or positive side battery cable off and bridging the cable to the battery post with the DMM set to AMPS. If you have an OEM radio, you'll need the code to reactivate it, so make sure you have that before doing anything. NOTE while doing this, do not attempt to start the car or turn on any heavy amp draw accessories...you'll fry the meter. Also, remove the bulb from the trunk light or you'll get a drain reading from that. Don't leave the doors open, either, or you'll be reading the interior light load. Let the interior lights dim out before beginning the test. Open the hood and the cover over the fuse panel under the hood.

This test is a lot easier with two people...one watching the meter and one pulling and replacing fuses.

With the meter set up correctly you should be seeing a drain of less than one amp. Begin by pulling ONE fuse and observe any change in the meter reading. If no change, replace the fuse and go to the next one. If there IS a change (drop in the reading) note which fuse it is and how much the reading dropped, and leave it out, but make sure you know where it goes. Continue pulling, checking and replacing (or leaving out) until the meter shows NO drain (000.00). Look back over your notes to see which fuse had the most drop. That is most likely your culprit. Your OBC is going to draw a tiny bit (less than 30 milliamps), which is fine. That's perfectly normal. You're looking for a drain of .25 amps an up.

My guess is it's going to be a faulty door microswitch that sometimes doesn't open the circuit when the door is shut.
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Old 10-13-2014, 12:19 PM
sausalitoroman sausalitoroman is offline
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Join Date: Dec 2012
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Mein Auto: 528i
Solved

Thanks for the tip. Without the meter I pulled a couple of fuses at a time while recharging the battery. Got to the cigarette lighter fuse and after removing the fuse. No more battery drain.
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