Internal fan constantly running

[vanondemand]

I have an 01 x5 problem is when I turn off the engine/car I can hear a fan running constantly from inside the dash board. It's not the engine fan or anything and can be heard faintly running even when the car is locked. It's been causing the car to run out of batteries making me have to constantly jump start it, it's not the battery because I just had it replaced.
The dealer told me its some kind of a/c control module that needs to be replaced for about $200 can someone help me !