I recently restored my '95 M3 to active duty after being parked for a year and a half, and while it runs great, suspension tight, etc., I am having a problem with the HVAC system: it seems that the right side is somehow stuck in "FULL HOT" mode, regardless of the temp knob position. When the upper middle vent control is put to Blue (cold only) and vent controls in the HEAT mode (feet), the driver's side temp seems to follow the knob position, but the passenger side seems to have heat all the time.

I read through Bentley a bit last night and see that there are temperature sensors on each of the two heat exchangers, presumeably to sense what temp is coming out of the exchangers and perhaps that is where the issue lies (higher resistance values suggest lower temp, so that if it were hypothetically "open circuit" it would be telling the control head that it's cold and therefore, pump more heat). I'm a little confused as to the role of the middle dash vent heat control has on the whole operation, so I'd like to find a good "theory of operation" writeup on the E36 "manual/automatic" (yes automatic, but not the later digital version) HVAC system.

Any suggestions on where one might be?

Thanks in advance, Mark