I have a 2006 1500 Silverado, 5.3L, that sometimes blows hot air when the A/C is on. Moving the temperature slide control does not affect the temperature. How I get it to work is that I shut the engine off and restart it. Then it works fine. I think its a vacuum problem but I cant seem to find a schematic of the vacuum system for the Silverado. If anyone has a copy of the schematic, I would appreciate it. If anyone has a similar situation and knows the fix that would be great too!