Pontiac Repair: A/C temp, grand prix gt, radiator support

Question
I have a 98 Grand prix gt that has the automatic temp control. At times the ext temp read out on the  will change temp on it own.

What I mean is if the outside temp is say 65 the readout on the auto temp control will start to go down and keep going down  some times all the way to -35. Sometimes it will come back up in a few minutes sometimes it will stay there.

My problem when the ext temp on the readout goes below 45 the A/c compressor will not engage.

I have replaced the outside ambient temp sensor.


HELP
Mike Shelburn

Answer
Hi,Mike
 This is a first,id like to find out more on this,usually what ive found with the ambient temp sensors is they will either show a blank display or it will be at -40 deg,i did some searching and what ive found was that there were a few complaints of this,one fix was a shorted wire that ran from the sensor to the ft body harness,trace the wires from the sensor to the harness making sure its not shorted to the radiator support or part of the fender or body,usually when a sensor drops to -30 deg the ckt or wire is shorted to ground,i would make sure your wiring to the sensor is ok.the other fix was a new control asm,the hvac control head had an internal fault that was causing this same problem your having,so if the wiring is ok,no shorts or opens,i would lean towards replacing the hvac control asm.keep me posted on this,because im curious on what you find out.Thanks


ED