Well my alt squeaks badly. Figured just the bearing. But if I turn on one heated seat the headlight dim noticeably. So the alt is on my light of projects. Probably rebuilt it. The brushes on it are fine. I had removed them and cleaned all the contacts as well as cable ends. In fact I did any and every cable end in the engine bay I could find.

But if electrical, why would a "reboot" of the car fix it? And it certainly fires up nicely.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car