The usual suspect of bad alternator is the combination of loss of spring pressure on the brush and enough debris or enamel buildup on the slip ring. Just a good bump the right way and you can probably get another 1000 miles.

When I removed mine I discovered it failed from brush dust buildup it just needed a cleaning. However I already bought the new one so I'm keeping the old one as an emergency spare I do have two e53.

Anybody within a couple hours drive of me could take advantage of the spare should it come in helpful.

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