If you unplug the connector from the low side the little round drier thing near the battery and jump a piece of wire I used a paperclip it will start the compressor up if it can run.
I used this method to get mine to take enough refrigerant to start the recharging of the A/C process.
You don't want to keep it in there just let if go for short 30 second bursts or so until the A/C can work on its own.

The kit I bought came with two bottle that contained all the oils and leak stuff in them has worked great the whole summer and having no idea how long it was empty before it was a project WJ I am just happy it worked.
Kit was like 30$ and I topped off my other WJ also since I had extra really worked great.
Seen no leaks at all and saved me from a expensive repair is it as good as the dealer or shop I don't know but it worked for me.
https://www.amazon.com/Interdynamic...g/dp/B001810SHA/ref=sr_1_1?ie=UTF8&qid=1480971370&sr=8-1&keywords=arctic+freeze

 

what year and engine do you have? If you have a 4.7 from 01-04 I wouldn't jump what you think is a low side switch? It's actually a pressure transducer

 

Its a 99 4.7 and I think your right its regulates the pressure but I needed to get the compressor to spin to charge it up and was the only way I found to do it.
Its been great through one 100+ degree summer of use zero leaks no blowouts so was worth it to me to try.
I am pretty sure they all work the same way but could be wrong just remember finding this somewhere and it did the trick.
The refill system has a pressure gauge on it so you can watch it and not overfill it the filling is the same way the pros do it maybe not the equipment but there is only the one fill port that I know off.
This was a 1k jeep I wasn't spending possible hundreds to get the A/C looked at its a cheap project and I don't worry about messing it up to much lol.

 

Thanks for the input.. its a 99 4.0. Ill take a stab at it. I looked at the local advance auto and the link to that one on amazon was a lot cheaper. I used the same stuff on my last WJ.. it was running but not cold so I didnt need to jump the compressor. My buddy has a fancy sniffer device for AC leaks so Ill swing by his place with some beers and talk into sniffing for me. He found my last leak in my WJ in about 2 beers.

 

If you just want to force it on, you can pop the relay out and jumper the contacts there that the relay would close when energize. Just need a short wire with a couple of 1/4" male terminals.

As I learned the hard way when chasing my WJ's AC woes, you should probably also test the resistance from the appropriate pin in the relay socket to the matching pin in the connector that plugs into the coil. On my '03 V8, there is a large connector up on the passenger firewall that had loosened just enough to cause high resistance on the circuit, and wouldn't pass enough current to actually make the coil engage the clutch.

 

Thanks for all the help. Today I picke up one of those DIY charge kits today.. I know it's not
Going to the leak but at least it got my compressor to kick on and now I have the eye in the system and I can try to find the leak. Hopefully I can trace the leak, change the bad parts and vacuum and charge the system correct.

 

Schrader valves or EVAP you said "eye" but guessing dye. If it leaks out and can't find it. EVAP and start crying.

 

Wait.. why cry? Is the evap in the dash? Sorry I Meant dye. I've put 100me on it running the A/C so once it gets dark I'll check. Luckily I parted out a wj years ago including the dash so I have a pretty good idea of what to look forward too I figured I'd donthe evap core and blend doors while I have it out. I may even throw a heater core in for good measure.

 

Wait.. why cry? Is the evap in the dash? Sorry I Meant dye. I've put 100me on it running the A/C so once it gets dark I'll check. Luckily I parted out a wj years ago including the dash so I have a pretty good idea of what to look forward too I figured I'd donthe evap core and blend doors while I have it out. I may even throw a heater core in for good measure.

it's not fun pulling the dash to get to the heater core.

 

Im sure its not but the blend doors are already broken so it make sense just to pull it all and do the core, evaporator and doors while its out. I put some dye in the system when I charged it and can't find any leaks in the engine bay so Im assuming its leaking in the cabin.