hhhmm interesting. I'm assuming that the switches are wired in parallel. Maybe you could try replacing the freon pressure sensor first as that is the one that triggers my fan. My engine's water temp rarely reaches 100C+

on a warm day (70F+) the aux fan would definitely come on after a while if the A/C is on and switches a few mins after the A/C is switched off.

One more thing to check is the aux. fan relay! It's called the ice cube relay or something due to its ice-cube shape. It's under a box on the driver's side wheel well (in the engine compartment obviously).

See if you could find that. Maybe it needs replacing!

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2008 BMW 335i Coupe