So I got my AC up & working back in 2014 ,only used it a few times on some long trips to shows. Last time I turned it on the pump clutch wasn't engaging thought a bad compressor, so tested the other day will engage if 12volts is feed to it,so suspect the system is low & the low pressure switch is open. Today will test for any present pressure than evacute the system & recharge,hope this fixes the problem.