I have a 2010 and set the rear on manual when no one is in the rear.
You can set the fan speed to low that way.
I leave the Idrive setting alone so the rear passengers can adjust it
themselves - kinda why I bought it!!!!!!!!!!!!!

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Current - 2010 X5 35d
Retired - 2008 X5 3.0
Retired - 2007 X5 3.0
Retired - 2006 325 3.0