Over time, I began to notice an occasional grinding / rattling noise coming from my engine. I realized that it was coming from the compressor. Sometimes it would make noise when the AC was on, and then turning it off would make the noise stop. Other times it was the other way around. I looked at it when it was making noise and saw that there was a considerable amount of wobble in the pulley when it was making noise. One day it was being particularly noisy. I got home, inspected it, and found that the nut that holds the clutch plate had fallen completely off and the clutch itself was just dangling on the end of the compressor shaft.

I removed the pulley and discovered that the bearings were completely trashed. I could hold the pulley in one hand and wobble the bearing around quite a lot with the other. Since a used compressor was cheaper than a new pulley and cutch, and since I figured there was a chance that the compressor itself could still be bad, I ordered a used compressor, planning to use just the pulley and clutch. When the compressor arrived, I found no wobbling in the pulley at all.

I just finished putting the pulley from the new (used) compressor onto my car (97 Civic, in case it's relevant). However, on my existing compressor, the replacement pulley wobbles a little. It seemed to fit nice and snug on my existing compressor, yet I can wobble it about 1/16th of an inch or so, even though it didn't wobble on the compressor it came with. Undeterred, I put it all together and started the car with the AC running. Everything was fine - no grinding noise, and the AC was blowing cold air. I turned the AC off and instantly it began making the same grinding noise as before, and smoke started coming off of the pulley.

This is my first time working with a compressor and I'd love to get some more expert thoughts on this. I did have to tap the new pulley on to the compressor with a rubber mallet - I wasn't hitting it very hard, but I'm wondering if I could have messed something up when I did that. I don't think the pulley should have any wobble in it at all. I'm speculating that when the clutch is disengaged, the pulley is wobbling slightly and grinding against the clutch, creating the friction which is generating the heat that's causing the smoke.

Should I try putting another shim behind the clutch? Any other thoughts on why the new pulley would wobble on the existing compressor but not on the one it came with?