I had both climate control ***** set on cold (all the way blue) and the fan control set at 3. Everything was fine for about 15 minutes, then the passenger side vents started blowing out hot air. I turned on the ac and cold air started to blow on the driver's side but hot air continued to blow on the passenger side. I moved the switches, (both climate control and fan speed, turning on and off ac), for about 10 minutes and the only way I could stop hot air from blowing out the passenger side vents was to turn the fan off. I continued driving and about 15 minutes later I set both climate control ***** on cold (all the way blue) and the fan control to 3 and it was fixed. I then moved the switches, (both climate control and fan speed, turning on and off ac), for about 10 minutes and it was still fixed. At no time did I turn off the car. Does anyone know what could have caused this?

 

Hi. Did you ever figure out what caused this? I have an '04 and it's done the same thing 2 different times.

 

Not exactly. I did however have to take it in to get the fan control speed **** fixed because the blower kept turning on and off at random times. They had to order a part and I'm waiting for it to come in, but I don't know if it is related or not.

 

I just replaced the fan regulator for $146 - genuine/new Benz part. Chrysler wanted $495 for the same part. It might be worth the research. There are dozens of MB parts dealers online.

 

There are stepping motors that controll the heat blend doors for passenger and the drivers sides, the passenger one may be binding up and not fully moving the door, or the flap is sticking at times, or could be the controller itself, the fan controller I think just controlls fan speed.

 

Bingo, unlike older cars, the passanger side ducting and drivers side ducting are seperated from each other, to include the ducts running up from the air cooler from the a/c and the heater core. Your passanger side is either binding, the flow control motor is kapoot or your temp control roller switch is sour.