My 95 z28's a/c was working "ok" for a long time,then suddenly the compressor clutch quit kicking on.I have no codes in the computer, and I am thinking that it just got low on freon. To check, I would like to jump wires and force the compressor to run. If the a/c is not cold, that could explain a low charge. I have checked the fuse and have swapped relays to no avail. So , what terminals exactly do I jump to force the compressor to run? Does the pressure switch have more than two connections? If so, which do I jump? Or, is it better to jump at the relay, and which connections would that be? I am hoping that I just need to run the compressor and put in a can of #134. What other things should I look into and possibly need to replace?
thanks , edman

 

Jump B1 to B4 in the AC relay..
That will run the compressor