rear Blower motor '91 Carrerra 2 964

[deykamp]

I didn't see my post.
Anyone know how to tell if the heating/AC unit control unit is bad?

[lucittm]

Many functions here. Does the fan control increase/decrease the speed of both fans? Does the temperature knob affect the mixing valve to add heat to the incoming air? Does the AC button energize the compressor clutch if there is suitable pressure in the refrigerant lines? Does the defroster button bypass the fan speed to the maximum setting and direct all the mixing valves to the windshield? Finally, do all of the functions work on the driver's side and the passenger's side?

I have found the servos on the mixing valves go bad before the control unit. There is a small fan in the back of the control unit that pulls in cabin air across the thermostat to regulate the cabin temperature. I think by now many of those fans have failed and the result is that the temperature change in the cabin takes longer.

If anyone has changed out the fan with the replacement, let us know. The part number is 964-659-148-00 and our host carries them for the paltry sum of $307.00!

Hope that helps,
Mark