2001 Ram, 5.9L, had it about a month now.

Shortly after I bought it, I noticed the air would start to make a grinding/chirping noise when the clutch kicked on, and it didn't seem to blow as cold. (The best I can describe the noise is like a chewbacca like noise that seems to happen when the clutch engages)

I took the truck in to my mechanic for some other small stuff I didn't have time for, and told them to check the AC over.

Went and picked it up and was told the AC was fine, no problems, good charge, etc. When I told him about the noise that I thought might be the clutch he said he didn't hear it when he had it. But if it was the clutch, just wait until it quits, and he'd replace the compressor then.

Since then I've realized the noise only seems to happen when it gets hotter outside. He looked at it first thing in the morning, and it was quiet then. That afternoon when I picked it up it started doing it. If I turn on the AC first thing in the morning, its quiet; afternoons it is noisy.

I'm going to change the belt this weekend, just for preventative maintenance, maybe that will help. Any other ideas? Would the AC clutch only make noise in the warmer weather if it was going out?

 

Mine does the same thing. It might be you water pump bearing though. Every time the AC clutch engages it puts stress on the belt, which puts more stress on your fan pulley (water pump). Open the hood and try to wiggle the fan pully back and forth, that might be your problem.