GM Repair Problems? Ask GM Repair Expert Now.
When the temp output is only correct on one side the of dash, this is most commonly due to a faulty Air Temp Actuator. This is a little motor that turns the door internal of the HVAC housing to switch between heat and A/C. The passenger's side actuator is located behind the glove box, mounted to the side of the HVAC housing (click here for image). Inspect the electrical connector and wire harness for any loose, broken or damaged wires. If the inspection checks ok, remove the actuator and turn the door pin by hand. The temp output should now be correct. If not, the problem lies internal of the HVAC housing. It will need to be removed, opened and the door inside repaired as needed. If everything checks ok, replace the Air Temp Actuator. If my answer has helped you, please help me by leaving a rating using the stars at the top of this page or accept the answer so I may be credited. If you cannot rate or do not see the rating stars, please let me know. You can ask follow-up questions after you rate.