Okay, this is my first post, but have tried to familiarize myself with the site. I searched around a bit to find some useful info. Here is my situation. Last summer I notced that if I shut my truck off with the heat on then returned and tried to turn on the A/C, I would have to turn the truck off, turn the temp to cold, then restart truck. This worked to get the cold a/c on. Never had any trouble with the heat until now. I basically have no temperature controls at all now. The truck warms up to 210 with no issues and I have plenty of antifreeze. I noticed that my feet were cold despite having the floor/defrost on. I turned it to the vents and it was blowing cool air. The air does not change temp at all despite temp switch position (even with a/c on) when the fan is blowing full blast. I then noticed that if I turned the fan down to 1 it would get a little warmer. I can hear some action taking place when I turn the temp control, but it makes no difference in air temp. I searched around and found these threads, Which were somewhat helpful. http://www.gmtruckclub.com/forum/showthread.php?t=16703&highlight=heater http://www.gmtruckclub.com/forum/showthread.php?t=16756&highlight=heater The question I have is what part is likely bad, and how hard is it to change. Is it part 18, 22, 21 or?? in this schematic? www.gmpartsclub.com I am leaving for a 3000 mile round trip through the northern US in three days so I need this heat working. Thanks in advance and I hope this has not been answered a million times. Truck has manual controls and the 4.8L engine (the small v-8). Very basic work truck.