E39 rear fan runs with car off?

[iheartwebster]

I have a 2000 528i and the rear fan will turn on periodically for a few seconds and rest for about 15-20 seconds. It only does this after the car is turned off and the key is removed. I have tried turning off all electronic components before shutting the car off but it still happens on occasion and I can't see a pattern or reason why. Has anyone seen this before?

[kyleabaker]

My 1995 325is does this occassionally, but I think it has something to do with the system that cleans and purifies the air on the inside. There is a way to disable this if that's what it is, but I'm not positive if that's what's going on in your vehicle.