At idle all sounds good, when I turn the AC on, I get a constant chatter. It sounds like its coming from the power steering pump or somewhere between it and the engine. It’s certainly not the compressor which is on the opposite side of the engine. The source of sound radiation seems to be too high up to be the water pump.

Here’s a 26 sec video. It starts out with the AC on for the first 10 seconds, then I turn it off. At the 10 seconds later I turn it back on.
http://qik.com/video/0B5E894FF5E04953825DAA4C49C0A4B5

I tried videoing under the hood, but there was too much noise from the engine and fans to here the noise of mention, but the sound is absolutely not from the compressor or its clutch. I’m confused. Any ideas?

 

Is your belt kinda old or maybe a size too small? Have you done any maintenance/mods before having this issue?

 

I had the AC worked on a few times, but I believe this is a recent noise. Belts haven't been changed in the last 2 years.

 

sounds like a train w/out the choo-choo! lol

 

Have you looked at the electric fan? I am pretty sure those come on when a/c is on. I had a sound similar to that, and that is what it was... Worth a quick look anyways.