91 ac compressor

[leonard_nemoy]

First of all I tried searching but I couldn't find an answer. My 91 started making a weird noise from the belt area. Upon inspection it sounds like it's coming from my ac compressor. When looking at the compressor while the truck is running and the ac is turned off I can see the pulley spinning while the inside ring will turn about a half inch to an inch at a time. When I turn on the ac the inside ring spins equal with the pulley. What would cause this? I am thinking a bad clutch. The inside ring doesn't turn intermittently everytime I start the truck. It seems to only do it half of the time. Also the ac had not been ran for at least a month or two before the noise started. What could cause this issue without using the ac. It started the noise after a weekend of driving in extremely dusty conditions. And the ac still works fine. I had a hose and a few o rings replaced and recharged it with r12 3 years ago and it has had no problems until now. Thanks

 

[Alleycats]

Are you sure the 'noise' isn't coming from the idler pulley which is below the a/c compressor?

 

[leonard_nemoy]

Alright, I feel like an idiot I was 90 percent sure my noise was coming from the account compressor especially because the inside was moving a little when it wasn't supposed to be. But I borrowed a stethascope to double check and it does seem the noise is coming from the idler pulley below the compressor. But sense were in the topic should I be worried that my ac compressor turns a tiny bit when not engauged?

 

[Alleycats]

I'm not an a/c expert, maybe someone else more knowledgeable in that area will chime in?