I have installed a new A/C compressor, Clutch, evaporator, tube the works. New one was defective and immediately exploded inside when A/c kicked in. I had to again to replace the entire system . I bought a name brand instead of Advance Auto brand and installed it. I then took truck to a reputable garage to have entire system cleaned out of all metal fragments and then recharged. My A/C then began to blow cold and then hot air. Garage installed a blender door actuator. When picking up my truck, I was told the heat door didn't completely close, so I was getting a blend of warm air with the cold.??? Anyway, it worked but was not really very cold. A year in and now the truck blows very cold, then switches to very hot air. I tried to recalibrate the actuator, but I still am having this issue. Any suggestions? It is a 2001 but there was not a topic for my year of GMC and 1999-2003 are supposed to be the same.