How to replace AC belt tensioner chevy silverado (easy!) 

Immediately after installing it? Or after driving for over an hour?

@@HandsOnDismantler when I bought the truck the ac belt was off I put it on it makes a horrible noise but the ac works. Then the belt came off I replaced the tensioner hoping would help the noise along with the belt. Nope belt still comes off and still makes a chirping noise

Definitely sounds like the previous owner knew about the issue. Was it a market place purchase? Or did you get it from a friend? If someone you know you could ask what the issue they had was? But sounds to me like the ac compressor is shot. The air might be cold but it might not be AC cold. Even if it is. The bearing could be shit causing the belt to slip. There’s also a tsb related to the ac compressor causing a jerk in the belt, (noise and damage to the tensioner occurs)

@@HandsOnDismantler Lol good ol Market place its a solid 2002 2500HD