A/C issues

Hey all,

Here is my latest dilemma. Yesterday, I started my car w/AC on when leaving a restaurant. I heard a grinding noise coming from somewhere. At the time I thought it was from under the hood but it wasn't all that loud. When I turned the A/C off, the sound went away. I drove home w/no problems with the A/C off. While in my garage, I wanted to reproduce the sound and see exactly where it was coming from. So, I turned the A/C on and went to check. The sound happened for a second or so, but by the time I got out to look, it had stopped. Since then, no more sound. Here is what I see now. The compressor cycles about every 20-30 seconds. I have one of those $30 refill kits with a guage. The pressure seems to build up to around 55psi then the clutch/compressor turns on and the pressure starts dropping until it gets to around 20psi when the clutch/compressor turns off and the pressure builds back up. I don't know how accurate the pressure guage on those units are though. Also, now the A/C is cold on the passenger side and not cool on the driver side.

Any advise would be helpful. How would I check to see if the compressor went bad? Would an actuator in the mix bod going bad make a grinding noise? I'm not opposed to buying a high pressure/low pressure guage setup..so I may do that today. Also, if I'm adding 134a, how can I tell if it's building pressure. I wouldn't expect it to cycle so quickly if it had enough refrigerant.

Thanks for the help!