This past summer the compressor went out and I had my local shop replace the entire system. New compressor, accumulator, etcetera. It worked flawlessly for the entire summer. Recently, I have needed to run the defrost since the above normal temps and rain have been making the windshield fog up like crazy. The switch for the AC lights up, the engine revs like the compressor has kicked on, but the compressor will not run. I jumped the low-pressure switch and all that did was make the engine rev like the compressor had kicked on, so I assume that it's working. Would the relay be at fault? I had one of those DIY refill gauges laying around, so I connected to the port, and it shows high pressure. Any help greatly appreciated!

 

Get a volt meter. It either has power or it doesn't.

 

Power comes from the switch to the relay to the low pressure switch to the compressor - should be easy to follow the power with your $5 test light or $10 voltohmeter