I picked up a 89 535 with 265K miles and it runs great. AC works fine except for the driver's side blows cold and the passenger side blows hot. The temp selector knob on the pass side does rotate the switch but has no discernable effect. I suspect the control, or a air control stepper motor is defective or a duct has come loose. Has anyone come across this or suggest how to proceed?
Air conditioning blows hot on one side I performed the test of clamping off the heater hose and the pass side started to blow cold air. I finally got around to replacing the heater control valve (used part) and now both sides blow cold. i then changed the temperature setting on the drivers side and it started blowing hot but would not go back to cold when I returned the temp setting to cold. I have to unplug the leads to the solenoid in order to "reset" the drivers side to blow cold again. Hmmmmm. I guess it is possible that the second HCV is faulty or is it something else?