Well, i hav a 98 blazer lt 4x4 n im havin the same problem. I discovered that my actuator always wants to turn towards heat. Found a bravada in a junk yard with the auto CC n pulled its actuator... still does the same thing. Do you think i got ANOTHER bad part? Or maybe a bigger problem somewhere else?

 

Pull the actuator(s) apart and see if the big plastic gear on the output shaft is cracked or is moving independently of the output shaft. It seems that if the actuator cant find a stop to work against ( because the gear is cracked or slipping) it goes back to its default location. Sux that that is HOT!