Noise from some a/c related part

Hi, new here. And I'm about to show I'm somewhat ignorant about my truck when it comes to the a/c. To be honest, when I was younger and worked on my own vehicles ('80s) I never had a/c, so this is new to me.

A month or so ago I was driving my '97 Silverado C2500 and I heard a noise I hadn't heard before. It almost sounded like a fan cycling on and off. It would be on for a few seconds, then off, then back on for a few seconds. It's not always engaging, but it never stays engaged for more then a few seconds - 5-10 max.

Anyhow, I tracked it down under the hood to some pump looking device run by the main serpentine belt. Based on the pic of the belt routing under the hood, I figured out it has something to do with the a/c. I'm thinking this maybe the compressor?

So the noise is caused when this device engages. I can tell as the noise starts when what I'd describe as a plate begins turning and stops when this plate stops.

Hopefully I've described this well enough without soundling like a complete moron. Can anyone provide some insight into what this noise indicates? Bad compressor (assuming that is the compressor)?

Thanks in advance!

It is very hard to diagnose noises, especially when we can't hear it or see it.

There is a clutch on the front of the ac compressor and when the clutch engages, the compressor turns and compresses R134a. Is the noise coming from the clutch or the compressor? A/C clutches do go bad (ask me how I know, mine went out at 80 MPH and took out the compressor - $$$) and they can be replaced without removing the a/c compressor.

Also make sure the belt is not slipping due to a weak tensioner when the a/c kicks on.

//2000CAYukon

It is very hard to diagnose noises, especially when we can't hear it or see it.

There is a clutch on the front of the ac compressor and when the clutch engages, the compressor turns and compresses R134a. Is the noise coming from the clutch or the compressor? A/C clutches do go bad (ask me how I know, mine went out at 80 MPH and took out the compressor - $$$) and they can be replaced without removing the a/c compressor.

Also make sure the belt is not slipping due to a weak tensioner when the a/c kicks on.

//2000CAYukon

Thanks Yukon. I knew without hearing it I wouldn't be able to get a definite diagnosis, but I hoped I explained it well enough that I could get some ideas. I took the truck in for an oil change today (can't do oil changes here in suburbia when your driveway is on a decent slope like mine) and wouldn't you know it - no noise. I tried running the a/c on the way to the garage to see if it was working. After running the a/c, no more noise!

i was browsing the forums and came across this. i know this is a bit late but i have a question as well. the sound when your power steering pump goes out. that tell tale whine. well i heard it, swapped the pump, and only half of it went away. i then realized that the ac was making the same darn noise. now my question is this, that noise, is it caused by the compressor or the clutch? and if it is the clutch, how easy/hard is it to replace one of those? could it be anything else?

i was browsing the forums and came across this. i know this is a bit late but i have a question as well. the sound when your power steering pump goes out. that tell tale whine. well i heard it, swapped the pump, and only half of it went away. i then realized that the ac was making the same darn noise. now my question is this, that noise, is it caused by the compressor or the clutch? and if it is the clutch, how easy/hard is it to replace one of those? could it be anything else?

Does the noise happen when the compressor is on or off (or both). The clutch is pressed on and can be replaced without draining the system. Try to determine where the noise is coming from (body of the compressor or front). Also make sure the tensioner or idler pulley are not making the noise.

//2000CAYukon

Spray your clutch with silicon or WD-40 and see if the noise stops same with the belt tightener squirt a little in it and start it up to see if she quietens down

ill look into it within the hour, it stays making noise both on and off... (ac on and off)