The ATC/AZC system can store fault codes that may be helpful. A specialized scan tool is needed for this, a standard engine code reader won't do it.
Make sure that the IR interior temp sensor is unobstructed or hazed over with dirt, nicotine or armor all-type spray residues. It should be located between the zone temp control knobs.
The system can be reset (this will also erase any possibly helpful fault codes) and recalibrated. Remove the IOD fuse. If the fault codes are real, they will come back. Remember to reset your clock when finished.
The HVAC control runs a five second calibration cycle when the IOD fuse is inserted at PDI. If the ignition key is cycled within that five second window, the calibration cycle aborts. The result is a HVAC system that does not accurately measure temperature. Customers may describe erratic temperature control, hot air with AC settings, cold air with heat settings, or different temperature output for driver and passenger from identical settings. The repair procedure is simply to 1) remove the IOD fuse 2) reinstall the fuse 3) wait five seconds before cycling the ignition key.