STI 18729 - Manual (Page 12)

© 2010 Pentair Technical Products 89059119 - 12 -
TROUBLE SHOOTING
Basic Air Conditioning Trouble Shooting Check List
1. Check manufacturer’s nameplate located on the unit for correct power supply.
2. Turn on power to the unit. The evaporator (Enclosure or “COLD” air) fan should come on. Is there
airflow?
YES, proceed to step 3.
NO, possible problem:
• Open motor winding
• Stuck fan motor
• Obstructed blades
Repair or Replace
defective part
3. Check thermostat setting and adjust thermostat to the lowest setting. This should turn the condenser
fan and the compressor on. Did condenser fan and compressor come on when the thermostat was
turned on?
YES, proceed to step 4.
NO, possible problem:
• Defective thermostat Replace part
4. Are both fans and the compressor running? If not the unit will not cool properly.
5. Check condenser (Ambient or “HOT” air) fan for airflow. Is there airflow?
YES, proceed to step 6.
NO, possible problem:
• Defective thermostat
• Open motor winding
• Stuck fan motor
• Obstructed blades
Repair or Replace
defective part
6. Carefully check the compressor for operation - motor should cause slight vibration, and the outer case
of the compressor should be warm. Is the compressor showing signs of this?
YES, wait 5 minutes, then proceed to step 7.
NO, possible problem:
• Defective thermostat
• Defective capacitor
• Defective overload
• Defective relay
Repair or Replace
defective part
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
Repair or Replace
defective part
8. To check for a bad thermostat, turn power to the unit off. Remove the control box cover and place
both thermostat wires onto one terminal (replace control box cover for safety). This will activate
the switch in the thermostat. Turn the power on and if both fans and the compressor come on, the
thermostat needs to be replaced.