I just recently bought my 2000 e39 M5 with 85k miles. Last week was pretty muggy at night, it was very humid. i put the windshield defroster on cold but only heat came out?? very weird, so i just said ill check it out later , maybe some AC/Heat flap is stuck (if the is a flap), still very new to this car. So 2 days ago i was using the ac (cold) and the car was still very hot, so i changed the distribution to vents and floor. 5 min into my drive the car is still hot!! it feels like a heat wave is coming from the back, i just thought the car sat in the sun for too long. The car was getting warmer inside so i put my hand in the back floor and felt heat.??? So i was getting A/C from the main vents and HEAT from the floor. Then i changed it back to just the main vents and the A/C was still blowing very cold. What should i be looking for?? is this a common problem for e39 m5?