Just learned that a lot of GM trucks with dual zone climate control have had issues with their blend door actuators for the AC system. A blend door is what regulates the temperature of the air leaving the vents. They can either be vacuum or electrically operated. A clue to this may be that the temperature on one side may not match the other side (hot, or warm when it is set to cold). I was fighting an issue with my AC just not blowing very cold at all, and I feared the worst. But, I noticed on my way to work that the window and windshield on my passenger side were fogging up from the cold air. You just never think to check the passenger air coming out. I was able to reset the AC by disconnecting the truck’s battery for 30 minutes, reconnecting it, then turn the key to on, but do NOT start the engine. During this time, do NOT touch anything! Wait for approximately 1 minute, the truck will tell you to roll down the driver’s window, then back up. After 1 minute, turn the engine on. The AC system has reset itself, and should function as normal.