1. Check manufacturer’s nameplate located on the unit for correct power supply.

 

2. Turn the power to the unit on. The evaporator (Enclosure or “COLD” air) blower should come on.

Is there airflow? 
YES, proceed to step # 3.
NO, possible: Open motor winding or stuck blower motor, obstructed wheels/blades

 

3. Check thermostat setting? Adjust thermostat to the lowest setting. This should turn the condenser

blower and the compressor on. Did condenser blower and compressor come on when the thermostat was turned on?
YES, proceed to step #4.
NO, possible: Defective thermostat

 

4. Are both blowers and the compressor running? If not the unit will not cool properly.

 

5. Check condenser (Ambient or “HOT” air) blower for airflow. Is there airflow?
YES, proceed to step # 6.
NO, possible: Defective thermostat, Open motor winding, Stuck blower motor, Obstructed wheels/blades

 

6. Carefully check the compressor for operation - motor should cause slight vibration, and the outer case of the compressor should be warm.
YES, wait 5 minutes, then proceed to step #7.
NO, possible: Defective thermostat /Defective capacitor / Defective overload / Defective relay

 

7. Make sure the coils are clean. Then check evaporator “air in” and “air out” temperatures.

If the temperatures are the same:
Possible loss of refrigerant
Possible bad valves in the compressor

 

8. To check for a bad thermostat. Turn power to the unit off. Remove control box cover, place both
thermostat wires onto one terminal (replace control box cover for safety). This will pass the switch in the thermostat. Turn the power on. If both blowers and the compressor come on, the thermostat needs to be replaced.