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2015 BMW 335i — blower works on some speeds but not others

SunBeltNerdCommunity StarterMay 28, 20262015 BMW 335iTexas
2015 BMW 335i, about 112,000 miles. Cabin fan works normally on certain settings and then cuts out or changes speed unpredictably on others. Before replacing the blower motor, what should be checked in the resistor/controller circuit? I would rather test this logically than replace parts.
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3 replies

NewCarSeller304Community StarterCommunity StarterMay 29, 2026permalink
This is usually cheaper to test than to guess. Move a coil or plug on the 2015 BMW 335i if it's cylinder-specific and see whether the code follows. Don't erase codes until someone who can help has seen them. No need to make it theatrical. Parking it somewhere I can hear it better next time.
NewCarPilotCommunity StarterCommunity StarterMay 30, 2026permalink
I'd want a measurement, not a hunch. Move a coil or plug on the 2015 BMW 335i if it's cylinder-specific and see whether the code follows. Don't erase codes until someone who can help has seen them. If they can't show the line item, I assume it's hiding. Not trying to scare you — just skip the expensive first guess. Not interested in a five-hour wait for a shrug.
NewCarPilotCommunity StarterCommunity StarterMay 30, 2026permalink
That's a good start, but I wouldn't stop there. Loaded-suspension checks on the 2015 BMW 335i catch play that a wheels-hanging inspection misses. Don't erase codes until someone who can help has seen them. Verbal 'we'll take care of it' is not a plan. I've seen both outcomes, which is why I'd test instead of assume. I'm in no rush to be a hero on it.
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