CMW126

Recently purchased a 1985.5 944 that has a problem with hot air blowing while the AC is engaged. Upon the initial start up and while idling the AC blows cold. But this changes when the vehicle is driven as full hot air blows from the vents. I checked the heater clip and it is fully functional and intact. I changed the vacuum check valve. Still no change.


I also ran the vehicle to the point where hot air was coming from the vents and then let it cool down. I waited 10 minutes and I then started the car and turned the temperature to cold and turned the AC on. The AC blew cold; however, as the car ran and the engine heated up the damper linkage change on its own (without me changing the temperature control) and heat started coming out of the vents.

Could the issue be a bad heater control valve? Or bad solenoid?

Any suggestions would be appreciated, thanks.

mytrplseven

There is a "freeze protection sensor buried deep in the evaporator core that turns off the A/C compressor. If that sensor is defective, it could lead you to believe it's a heater issue. The A/C will start up cool and then, because of erroneous tolerances on the sensor, will act like there's frost or ice in the evaporator core. the sensor is accessed from the footwell near the accelerator pedal. The sensor connector and attached capillary tube is shown in the illustration below. When the capillary gets cold it opens the circuit to the A/C relay, shutting down the compressor. This may or may not be the solution to your problem but is worth investigating further.

CMW126

Thank you!