More than likely, you have a fault with a temperature actuator. The one that deviates from requested, would be the one suspected. There would be a fault code in the system, that would confirm this. Try this actuator recal procedure and see if it restores normal operation, this may be temporary.
Use the following steps to perform the calibration update:
Turn OFF the ignition.
Remove the battery positive voltage circuit fuse of the HVAC Control Module.
Important: The module memory will not clear if the battery positive voltage circuit fuse is installed in less than 60 seconds.
Wait 60 seconds.
Install the fuse.
Wait 60 seconds before moving the HVAC controls.
The fuse that powers the HVAC module, is the DIC/RKE fuse in the RH junction block, behind the right side instrument panel access panel. I am not sure what the collateral may be for removing this fuse, since it has the letters RKE in the heading. It may lose the remote keyless entry programming.
Tuesday, January 1st, 2019 AT 6:02 PM