I had an oil leak that exacerbated the problem worth worn out brushes and slip rings.

Search for the valeo slip ring and brush kit it was $20 when I bought mine. If you are fairly handy it's 5/10 difficulty at worst. If you do brush only with polarity swap 4/10.

I did the brush and rings swap on my car, did brush and polarity fix on wife's.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)