Climate Control spews hot air on driver and cold air on passenger. This happened since the vehicle was new and was always corrected by shutting engine off for a few minutes and re-starting. This "fix" now lasts only a few seconds. I disconnected the battery overnight and now have no control over the HVAC except blower speed and on/off. Hot air comes out defrost vents while in auto or manual mode at 60 deg. AC temp setting.

I have searched for help and found references to replacing actuators (apparently there are three), involving some "recalibration" and not specific enough for me to follow. Information on this site suggests $995 cost with the dealer service route, along with multiple trips to get it done. This would not be acceptable.

Can anyone suggest how I should proceed to resolve my problem?

This only happened when the A/C was turned on. The A/C would blow hot air instead of cold air into the cabin. The only way to correct it is to turn the vehicle off and restart. The climate control would work inconsistently, sometimes delivering cold air, others, burning hot heat hotter than the fiery depths of hell. Inconsistent so it took 4 visits to the GMC dealership. But once it occurred, the dealership found it and determined it was a defective climate control actuator. The cost to repair was $995, and took 2 days to fix.

Now it works better than before, giving me and my butt nice, cool air instead of Satan's African desert of death. That may have been a little extreme, but it sucked. Note: trying to outsmart the system by turning full heat only results in the feeling of being in a convection oven, there is no improvement, best thing is to restart, or run away.