A couple of questions and suggestions. Does the a/c completely quit working or does the air temperature out of the vents increase some? Stick a thermometer of some type in the vents to get a real reading of the air. If the high pressure switch or trinary switch is opening due to high or low pressure you can check that. When it operates it kills the 12 volts to the compressor clutch. Use a voltmeter or 12 volt bulb with a couple pieces of wire to check it. Clip one wire to the wire going to the clutch and the other to ground (don't interrupt the circuit). When the a/c is running you will get 12 volts. If the trinary opens the voltage will drop or the bulb will quit burning. Remember that with a working a/c the thermostat will interrupt power to the clutch also. Good luck.

Six volt guy living in a twelve volt world