Suction (Low 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 expansion valve and low pressure line. If valve is not frosted, low pressure line is not cold and low side gauge indicates vacuum, check for leaking thermostat or frozen or defective expansion valve.
3. If discharge temperature is low but air flow is abnormally low, check for frozen evaporator.
4. Inspect expansion valve. If valve is frosted check for defective or restricted expansion valve.
5. Inspect low pressure hose. If hose is cold near compressor, check for collapsed or restricted low side hose.