GM-GMC: 1/2 hot, 1/2 cold, technical service bulletins, chevy 2500hd

Question
I have a 2004 Chevy 2500HD truck.  The driver's side vents will suddenly start blowing hot air, while the passenger side continues to blow cold.  I can turn off the engine, and it will reset and blow cold again, for a while.  There is no set amount of time for it to run before it goes out.

Answer
Hmmm, the proper way to go about diagnosing this concern is not really one that can be done without a scanner.  There are temperature sesnors located in the air delivery ducting which allows for the different temps from one side of the vehicle to the other etc. etc.  If one of these sensors is malfunctioning or if the control module misinterprets the data it recieves from one of the sensors than it will start to do strange things.  I checked for technical service bulletins, but there were none for that specific concern.  It isn't a cheap option but you if the problem persists you may need to have a shop with the proper scanner diagnose it for you.
Hope this helps a little.