A/C Compressor???

I have a '94 Sonoma 4x4 with 4.3L, I just got it this spring. Since I bought it the a/c has not worked, it won't blow cold air at all. I checked the compressor to see if it spun when I turned the a/c on, but nothing changes, and since this is my first vehicle with a/c, I dont have much experience with it. So I cant tell if it is engaged all the time or not engaging at all. I also recharged it, thinking maybe it was low, but that did nothing, and afterward I could hear a hissing sound coming from around the compressor somewhere. I checked all hoses from the compressor, and all others just to be sure, but none of them feel cold at all. I think it may be a bad compressor, which I am told is quite expensive, so I probably wont worry about it just yet, but I need to know if it is staying engaged all the time or not, cause that would drag down my gas mileage. It also makes a high pitched whirring sound from the compressor, but that may just be the belt also. So could someone please tell me how to tell if the compressor is running, or how to test it? It would be greatly appreciated.

for a good primer on a/c and a lot of good diagnostic steps go here: http://www.polarbearinc.com/Trouble1.htm

from an old post by Old Master

thanks, tomorrow i will start testing the coil and post what i find

Is this a R-12 or R-134a system?
To see if the compressor is running just watch the front clutch hub.

R-134a
I watched the front hub and nothing happens, so its not engaging, i will check the coil to see whats wrong with it, but replacing it will have to wait

R-134a
I watched the front hub and nothing happens, so its not engaging, i will check the coil to see whats wrong with it, but replacing it will have to wait

I would jump the low pressure switch first.
Low pressure is the leading cause of compressor not kicking in.
MT

ok ill try that tomorrow, i just gotta find it to jump it :uhoh:

Should be a two wire switch on the reciever dryer. Big can.