I'm having trouble with the HVAC system. Specifically the front in any mode that requires heat.

Most of the time, the heat does not work, on either side, in any mode. *Occasionally* the damned thing will blow hot, but only if it's set to 90• (if I set it to 89 or below I get no heat at all). If it works, it will continue to work throughout the trip, and will usually work for a few subsequent trips, then it will stop working and stay not working for several trips.

If I turn the truck off, restart, off, restart, off, restart - it will eventually start working.

Things I have checked - or ruled out by deduction.

1. The heater core is getting hot coolant.

2. The blend door actuators cannot be the culprit, as there is one for each side, and both sides experience this problem at the same time.

3. The HVAC system has been calibrated as outlined in the service manual.

4. The cabin air sensor aspirator has been disconnected with no change in outcome.


At this point I'm leaning toward the control panel itself, but I'll happily accept any suggestions anyone has.

thanks,

 

My '11 LTZ has a cabin sensor, and I would suspect that if you have to crank the temp. all the way up.
Clean all the module connectors with an electronic cleaner. Fretting corrosion is an issue with erratic operation. An do the BCM connectors also.

 

I agree with repairman54. I’ve had the same issue and the cabin sensors in the headliner had to be replaced.