The A/C in my 2000 Sierra Z71 blows hot air when I drive slow or stop from light to light. When I drive 70 plus mph it works better. It seems to work intermittently. I have changed the sensors. I thank that it could be the clutch. Can the clutch be changed and if so how difficult?

 

sounds like it needs a recharge...................typical syptoms of a low system charge

 

Yeah check the freon level, and also check the condensor to see if its dirty with a bunch of bugs.