I’ve had alternators go bad on BMWs going back to a 1974 2002tii (several times), so that is nothing new. The part about stuff not working somewhat progressively is definitely on our e53 X5 and newer ones. Not sure how far back that “feature” goes. I think it is annoying, because it makes it very hard to diagnose, say, a seat heater that seems to suddenly stop working or only work after driving 5 miles or so. But I can see how it gave you some comfort in this situation.

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Mike

2005 e53 X5 4.8is 169k miles
2018 f90 M5
2018 Volvo XC60