I have a 1998 Jeep Grand Cherokee with a 4.0 engine. My ac compressor cycles on and off within a couple of seconds. I tried to jumper the relay switch and add some freon but the gauge went to 0. Is the system overcharged? The compressor did kick in and stay on when I tried this.

 

I would believe that to be the relay, or a loose connection. I'd start with the wire that powers the coil on the relay, verify correct current going to it. Then, check the line and load voltage in and out of the contacts. Being that you jumped the relay, I'd say thats it. I would still check, I hate throwing parts at malfunctioning equipment to troubleshoot.

 

Take it to a shop and get it evac and recharged. You are gonna waste a ton of money trying to guess it yourself.