I have a 1992 full size blazer. It has a 5.7 liter fuel injection engine in it (stock). It runs good but whenever i have the ac or the defoster on the belt pops off. Without the engine running, i turn the ac on and it blows cold air. Also while the engine is running, thier is hardly no movement on the belt, when the ac is on it starts moving tons only on the ideler pulley untill it falls off. As you can see in the picture it pops off number 22. What is causeing this and how can i fix it? Please help it is now summer getting up to 95 degrees here and its killer. please help and fast.

 

Since the common thread here is that the A/C compressor clutch is getting engaged... It could be a combination of problems. If the A/C works ok before the belt gets tossed, I would think that it is a problem with the belt and/or idler pulley.

 

is it easy to install a new pulley?

 

I meant to say tensioner. If the tensioner is not holding enough tension on the belt, it can cause it to jump off. Check all of your pulleys for wobble or gritty turning to see if there may be a problem there, but I would bet that it is a weak tensioner.