Just bought a Frankenstein 2005 Jeep Grand Cherokee. 135k on the body and 90k on the engine.

I push on the AC button and I get the yellow light but the compressor does not spin. Is it possible when they yanked out my engine from the other JC that the freon bled out and they never replaced it? Will the compressor work with NO freon in it???

What should I check next?? Saw a YT vid where the guy said there is an inline box switch that, if bad won't turn on compressor.

This is my first post sorry if in the wrong section.

 

I have an idea. It may help? You could buy one of these and use the gauge to test your low-side psi, get an idea about it wether it is really low. Then, try filling it up if it is... Might make your compressor work if thats whats causing it? I know with recharging an a/c system these cans work really well it seems for a lot of people. I've used them for recharging my Camaros a/c before, and it worked perfectly by just following the directions on the can for me. It's not good to overfill though. More refrigerant isn't better. Too much of it, and it will have a reverse type of effect and make your a/c not cool well. It's probably worth trying if nothing else to just see what the psi looks like. You're supposed to bleed out the air in the system, or something else, some other steps involved requiring equipment to do it right so... Not sure about what all that involves?

I believe for sure if you are low on refrigerant, then it can definitely cause the compressor to not function correctly. Maybe switch on-off-on-off-on-off..., or not at all?

There is an electrical component switch or something involved in making the compressor work too. I'm not sure where to look for it?

And then there is also a shim in the compressor itself that can be removed to make it work again for a little while if its the compressor being out of spec causing it to not work to turn on, but I would go there last after checking and verifying the simpler stuff first.