Strange noise and pulley problem

My 9C1 Caprice is a used ex cop-car, it only has 41k miles on it but those may have been some abusive miles. A pulley on the engine, bottom left facing it, during idle spools then clicks and stops, then it continues spooling, is this normal? The pully has a silver plate on the front. There is also a rattling or grinding noise while idling up any incline or under very, very partial throttle; it sounds a bit like a soda can scraping across rusty steel, sort of hollow. Thanks in advance!

What year? What engine?

1995 Caprice Classic, LT1 5.7L.

The lower left (as viewed) sheave?

http://72.19.213.157/files/94EngineBay.jpg

That is the air conditioner compressor. It you see the clutch cyling on and off, that may be normal, depending upon the settings of the AC controls and ambient temperature.

Yeah, the pulley under the hose. I guess that may be right, it just sounded abnormal. Thank you :)

The noise you are hearing on moderate acceleration may be something completely different from the AC compressor.