How to replace the defrost thermistor in a top-freezer refrigerator

This DIY repair guide gives instructions for replacing the defrost thermistor in a top-freezer refrigerator. Attached to the evaporator, the defrost thermistor detects the evaporator temperature and sends temperature signals to the electronic control board. The electronic control board uses the defrost thermistor signals to control the defrost heater during the automatic defrost cycle. If the defrost thermistor fails, the control board won't control the defrost heater correctly, causing cooling problems in the refrigerator. If the defrost thermistor isn't working, replace it with the manufacturer-approved refrigerator part.

This basic procedure can help you replace the defrost thermistor in some Kenmore, Frigidaire, Electrolux, LG and Samsung top-freezer refrigerators.

Instructions

1. Shut off the power

Unplug the power cord from the wall outlet. Move your frozen food from the freezer to the refrigerator section during this repair. 

2. Remove the freezer shelf

Remove the spacer in the freezer shelf.

Push the shelf to the left to release the right side of the shelf from the holes.

Pull the shelf out of the freezer.

3. Remove the evaporator panel

Remove the mounting screws from the evaporator cover.

Pull the top of the evaporator cover down and unplug the evaporator fan wire harness.

Push the evaporator cover to the left side of the freezer and disconnect the green ground wire and the ice maker wire harness from the evaporator cover.

Pull the evaporator cover out of the freezer.

4. Remove the freezer harness

Note: The defrost thermistor is a component of the freezer harness in this refrigerator.

Unplug the wires from the defrost heater.

Release the defrost bi-metal thermostat and the defrost thermistor from the evaporator coils.

Unplug the freezer wire harness from the back wall and remove it.

5. Install the new freezer wire harness

Plug the new freezer wire harness into the back wall receptacle. Attach the defrost bi-metal thermostat and defrost thermistor to the evaporator. Connect the wires to the defrost heater.

6. Reinstall the evaporator cover

Position the evaporator cover in the freezer compartment and reconnect the ice maker wire harness and ground wire. Push the evaporator cover to the center of the freezer compartment and reconnect the evaporator fan wire harness. Position the evaporator cover over the evaporator and reinstall the mounting screws.

7. Reinstall the freezer shelf

Push the shelf into the mounting holes on the left side of the freezer compartment wall.

Slide the shelf to the right and reinstall the shelf spacer.

8. Restore electrical power

Plug in the refrigerator to restore power.