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BMW E30 M52 Swap Electrical Alternator problem

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    BMW E30 M52 Swap Electrical Alternator problem

    Hi guys,

    Finished my M52 swap almost. Engine is running fine. I only have the following problem;

    After starting the alternator became really hot and even I saw some smoke. After measuring there is a leakage current from battery to alternator of 3,5 Ampère. Ordered used alternator which looks like to be okay, but after starting again there was something wrong and I had a leakage current of 3,5A. 2nd alternator died..

    After studying electrical diagrams and measuring everything from the alternator up to the C101 connector all looks like tot be fine (no connections to ground, no big resistances).

    However, today I noticed that pin 1 of the C101 connector (the one on the stock body side from the E30) is connected to ground. Pin 1 from C101 is the charge light and in connection with D+ on the alternator when I connect the C101 to the engine loom.

    What is wrong here? Since with this short to ground I should also ruined my alternator before the swap. Or is there something different in the E30 320i (stock) engine loom which misses in the M52B28 one.

    Hope someone could help me since I am a bit desparate now and would like to go on street soon :)

    Still not solved...

    A new alternator with only the B+ connected from battery (so no D+ connected). All good before starting but after starting direclty another alternator died.

    I am thinking of that the starter does have a bad ground connection and is getting it's ground from the alternator. Then the current is running in the wrong direction whereby the diode bridges burn out immediately. However, I carried out the measurment below (in Dutch called a V4 measurement) and all is looking good. 12 Volt over the battery and 12 Volt over the starter. So no current loss.

    Anyone overhere an electrical specialist and could help me with this annoying problem..?