There aux fan only runs as needed. The AC won't run at all if the fan fails the startup test. A bidirectional scanner will run the fan at various speeds to test proper operation.

Usually aux fan will turn on as something like 220F if AC is off and 180-200f when ac is on but that's just a generic example. I don't know the rules at all for e53. I do know that I've gone months without the fan kicking on then weeks where It kicks on every day.

E53 has the mechanical fan and the aux only needed to suppliment when that's not enough airflow (eg stuck in traffic and hot out)

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