AC to Heat

[king kong]

I have 05 GMC Serria K3500 LT 85,000
D/A while driving with A/C on, when
you you hit a bump as small as a expantion joint,the A/C goes from full cold to full heat. I pulled the plugs on the right side of dash ,and cleaned them with tuner cleaner ,and I reprogramed the computor and that did not HELP! after about 30 or 40 sec the cold does come back, till you hit the next bump.

[rat4go]

I'd bet you've either got bad wiring/connection somewhere in the wiring from the the AC controller to the motor that controls temp, or a control door motor with bad internal wiring.

Checking connectors is a good first start - make sure you check the ones at the temp control motor and the back of the AC controller, too!


Good luck!

[r gomez]

mine did the same thing turned out to be the pressure switch for the compressor

[king kong]

100,000 miles and running stong,the problem was the insulation on the wire loom was rubbed thru behind the glove box