Control boards are often misdiagnosed—before replacing the control board, first check more commonly defective parts. If you have determined that all of the other components are working properly, replace the main control board.
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The thermistor monitors the freezer temperature and sends the temperature reading to the control board. The control board regulates power to the compressor and evaporator fan based on the thermistor readings. If the thermistor is defective, the compressor and evaporator fan may not run when necessary. As a result, the freezer may not freeze properly. To determine if the thermistor is defective, test it with a multimeter. The thermistor resistance should change in conjunction with the freezer temperature. If the thermistor resistance does not change, or the thermistor does not have continuity, replace the thermistor.
If the condenser coils are located within the freezer walls, the coils do not require cleaning. However, if the condenser coils can be readily accessed from behind or under the unit, you should clean them every 6 to 12 months by using a soft bristle brush (or a dedicated condenser coil cleaning brush) to wipe off the coils in a circular motion. A vacuum cleaner with a nozzle attachment can also be used for hard-to-reach areas.
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04 - Tappan Freezer Evaporator Fan Motor
The evaporator fan motor draws air over the evaporator coils and circulates it throughout the freezer. If the evaporator fan motor is not working, the freezer will not cool. On most refrigerators, the fan motor will not run when the door is open. To check the evaporator fan motor, open the freezer door and then manually activate the freezer door switch. If the door switch is activated, but the evaporator fan motor won’t run, replace the evaporator fan motor.
The start relay provides power to the compressor. If the start relay isn’t working properly, the compressor may run intermittently or may not run at all. If the compressor won’t run, the freezer will not cool. To determine if the start relay is defective, unplug the freezer and remove the start relay from the compressor. Use a multimeter to test the start relay for continuity between the start and run terminals. If the start relay does not have continuity, or if it smells burnt, replace it.
Confirm the freezer is plugged in and there is power at the wall receptacle. You can plug another small appliance into the receptacle to confirm there is power. If there is no power, check the circuit breakers and GFCI (ground-fault circuit interrupter) outlets, if applicable, to confirm they have not tripped, or inspect any fuses to confirm none have blown. Plugging the unit’s power cord into a ground fault outlet is not recommended, but such an outlet can be reset to restore power by pressing in the button on the faceplate.
Highly Likely
07 - Sealed System Problem
If all the refrigeration components seem to be working but the freezer is not cooling properly, there may be a restriction or leak in the refrigeration system. To determine this, you will need to remove the evaporator cover (not applicable to chest freezers) and observe the frost pattern on the coil. Note: The compressor, condenser and evaporator fans should all be running, and the condenser coil should be clean and have good air flow. There should be light frost on most of the coil. If the coil has frost or ice buildup in only one section, there is likely a restriction or leak in the system. This repair is expensive (maybe cost prohibitive) and should be diagnosed and repaired by a qualified technician.