Jeep Repair: A/C not working, jumper wire, jeep cherokee

Question
Hello,
 I recently purchased an 87 Jeep Cherokee 4.0 4x4 and I am in the middle of some repairs. On the a/c, the air blows warm only and the compressor clutch is not engaging. I was told by a mechanic that running a jumper wire did engage the air compressor. Does this usally tell you to check the a/c relay and or the a/c fuse? And if so which relay is it in the power dist. box? My cover is missing and it is hard to find info on a/c repair. Also what powers the orange wire that connects to the black wires that run into the air compressor?

Answer
Usually when you have to do that the low/high pressure cutout switch is bad. It is a switch in the high pressure side of the a/c system (small metal line) and usually has two wires coming out of it. That would be the first place to check. Also the compressor will not come on if the a/c system is too low on refrigerant.