I have searched the threads and I have found similar problems but none that seemed to have my issue. I have a 2005 GMC Sierra aka Silverado and I have from time to time had an issue with the actuator not working correctly and only allowing hot air to blow through while on AC at whatever temp setting. This usually can be corrected by turning the engine off for 15-20 minutes and restarting to get cold air again. Well now it is getting colder here and I have noticed that my AC is working fine, but I can only get heat through the vents with the fan **** turned off. And it is very hot air at this position, but when you turn on the blower, the air gets cooler. Not AC cool, but definitely not hot. Can the actuator be stuck in the wrong position as it would do sometimes with the AC? If so, why does it not correct itself as it did in the summer? What part numbers do I need to look for and any reference or instructions would be greatly appreciated. Thanks!