I need to jump an ac compressor in an 88 silverado. I've read many things on how to. But none of them give a plain simple answer. I know the relay is behind the glove box, but there's 3 more relays. Which one goes to the compressor? Any input is appreciated

 

If the ac system is low on refrigerant you may want to start there. If there isn't enough pressure the low side switch will not engage. You can try jumping the switch with a wire to see if that is the problem. Or if you're wanting nothing more than to literally make the clutch engage you can pull out a multimeter and test for ground at the connetor going to compressor. After finding which wire is ground and power you can run a jumper wire (with a fuse for safety) to the positive side of clutch and it should work if the ac clutch is good.