A/C Pump making strange noise

My A/C pump on my /94 GMC Sierra 4 by 4 is whining when it's not working. I think that a solenoid pulls in a clutch on the front of the pump when A/C is called for, and it's when it's just running without A/C that I really hear the noise. It could be a bearing in the clutch I am thinking. As I look at it, the front of the A/C pump has the main belt coming over it, and the body of the pump is behind the "clutch???"

Can anybody tell me what to do here, it's a cream puff truck with only 80,000 miles on it? Can it be lubricated, should I squirt oil into what looks like the clutch of the A/C pump? Or is it all internal and need to be taken apart or just replaced?

Most likely you'll need to replace the compressor clutch.

Rust likes to build up on it and the clearance becomes too small, and hits the compressor pulley.

If the sound goes away with the clutch engaged, then you don't have any issue with the compressor bearing.

Hope this helps.

Hi, Thanks for the note. The sound doesn't go away entirely when the A/C is running. Also..sometimes the A/C clutch cuts in and out when it is running....same problem?? Or is that normal? Is there any lubing I can do to help it along perhaps? Rust has certainly built up like you say.

If your clutch is cycling on and off you could be low on refridgerant. There is also lubricant that goes "inside" the system. you can buy it at a parts store, or take it in and have it serviced and it may solve both problems.