ok after some battery drain issues ,i noticed when i switch off the car and sit there for half a min the heater fan goes constantly on and off,so im gona change the fsu unit ,ive seen some threads on the location of the fsu but only on left hand drive cars, where is the fsu on a right hand drive m5??
i think he means the rest button, it only works when you swich the car off for some reason, i just pulled the plug out of the fsu so see what happens in the morning ,pain in the arse on a right hand drive car to get to the fsu,loads of stuff in the way .
I know that the Final Stage Unit is a common failure point for the aircon fan. I recently had the same classic symptoms just as we are having a spell of hot weather in the UK. Anyway the kids seemed to enjoy going down country lanes with the windows wide open...