Air blowing on windshield with car off - battery dead

[ahsm]

I came to my car from the gym today and noticed the air was blowing semi full to full blast on the windshield (car was off, key wasn't even in ignition). I tried to start the car and click click, dead battery. I pulled out the HVAC unit and disconnected one of the blue plugs and the air stopped blowing. Is it a defective HVAC unit? Ironically, this problem started after I took out the HVAC unit to clean some dust off the small fan inside.

The car is a 2003 540.

[Doru]

Cleaning the HVAC is probably coincidental. This is a typical FSU failure. Change the part with OEM, not aftermarket.