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42 Posts
Discussion Starter · #1 · (Edited)
Greetings all,
In troubleshooting repeated voltage regulator/alternator failures, I discovered a circuit that seems to be bleeding voltage into the chassis or something. I started by finding continuity between the positive battery cable (disconnected from battery) and the chassis and then rigged a test light to start isolating circuits.

I removed the negative battery cable (with the positive side connected) and put a 3 watt test light in line between the negative cable and the negative battery terminal. With the key off, the bulb was fully illuminated and I started pulling fuses until the bulb turned off. After a bit of confusion relating to the trunk lid and/or doors being open, I found that fuse 43 is the only one that makes the test bulb turn off. This fuse is for the Instrument Cluster Control Module and the On Board Diagnostic Port. I've pulled the fuse and the car operates just fine, including all the instruments but I still want to find the short in this circuit.

The key questions I'm looking for feedback on are as follows:

1. With the cables disconnected from the battery, there shouldn't be any continuity between the positive cable and the chassis right?

2. There shouldn't be any circuits that allow a test light to be illuminated under the circumstances I described above right?

3. If no and no, then how do I go about finding the physical location of the short on this circuit?

Thanks in advance everybody!

Case (2002 330i)
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