Discharge (High Side) Pressure Low

1. Inspect sight glass. If bubbles appear while system is operating and condenser is not warm, check for insufficient charge of refrigerant.
2. Inspect evaporator and low side readings. If outlet of evaporator is not frosted and low side gauge indicates vacuum, check for leaking thermostat, or frozen or defective expansion valve.
3. Observe pressure readings after stopping engine.
4. If low and high side readings equalize soon after engine is stopped, check for defective compressor discharge or inlet valves or leaking compressor seals.