Auto HVAC Stability
 

I've done a bit of searching but have NOT found any reference to my clients stated "issue"...

Auto/dual zone system in 03 Z06. Owner complains that HVAC in hot or cold does not "stay" at the desired temp on long trips.. ie. cold day, Auto mode set, temp set to 74. Cabin temp comes up to desired temp but after an hour or so the temp starts to drop off, Increase temp with left knob, temp comes back to comfort level.... time passes, temp drops off again. Same issue in the summer with AC, desired temp initially works, then as time passes, temp must be turned down further to maintain comfort... Owner has had this car since new & states this was NOT a problem in the past. Just this past year.

I will have access to vehicle next week & will be running diagnostics with my Tech 2, plan to check 134a pressure, feedback from temp control doors, external & internal temp sensors. Not sure really where else to start & wonder if anyone has ever experienced this.

Tia!
M...