The defrost thermostat (a bi-metal switch) prevents the defrost heater from overheating. Testing this component is crucial if your refrigerator is experiencing defrosting issues. Here’s a step-by-step guide to test the defrost thermostat.
Caution: Please read our safety information before attempting any testing or repairs.
Important Safety Notice: Before testing the defrost thermostat, unplug the refrigerator to avoid an electrical shock hazard.
Tools and Materials Needed
- Screwdriver (Phillips and flat-head)
- Needle-nose pliers
- Multimeter
- Safety gloves
- Warm, wet towel (for plastic molding removal)
Steps to Test the Defrost Thermostat
Step 1: Safety First
- Turn Off Power: Unplug the refrigerator to prevent any electrical shock.
- Wear Safety Gear: Wear safety gloves to protect your hands while working.
Step 2: Access the Defrost Thermostat
- Locate the Thermostat: The defrost thermostat is usually located near the defrost heater at the back of a side-by-side freezer or under the floor of a top freezer.
- Remove Obstructions: Empty the freezer, and remove the freezer shelves, icemaker, and any other obstructions.
- Remove the Access Panel: The panel covering the thermostat may be held in place by retainer clips or screws. Use a screwdriver to remove the screws or depress the retainer clips with a small screwdriver.
Step 3: Remove the Plastic Molding (if necessary)
- Inspect the Molding: On some older top freezers, it may be necessary to remove the plastic molding to access the freezer floor.
- Warm the Molding: Warm the plastic molding with a warm, wet towel to make it more pliable and prevent breakage.
- Remove the Molding: Carefully remove the molding without forcing it.
Step 4: Disconnect the Thermostat
- Identify the Wires: The thermostat is connected by two wires with slip-on connectors or a wiring harness.
- Remove the Connectors: Firmly pull the connectors or harness off the terminals using needle-nose pliers if necessary. Do not pull on the wires themselves.
- Inspect for Corrosion: Check the connectors and terminals for corrosion. Replace the connectors if they are corroded.
Step 5: Test the Thermostat with a Multimeter
- Set the Multimeter: Set your multimeter to the ohms setting (Ω) on the X1 scale.
- Test for Continuity: Place one probe on each terminal of the thermostat.
- Cold Test: When the thermostat is cold, the multimeter should display a reading of zero ohms, indicating continuity.
- Warm Test: When the thermostat is warm (40 to 90 degrees F, depending on the model), the multimeter should display a reading of infinity, indicating an open circuit.
Step 6: Interpret the Results
- Pass or Fail:
- If the thermostat displays zero ohms when cold and infinity when warm, it is functioning correctly.
- If the thermostat does not display these readings, it should be replaced.
Step 7: Reassemble the Freezer
- Reconnect the Wires: If the thermostat is functional, reconnect the wires to the terminals.
- Reattach the Rear Panel: Secure the rear panel with screws or clips.
- Replace Freezer Components: Reinstall the freezer shelves, icemaker, and any other components you removed.
Step 8: Restore Power and Test
- Plug in the Refrigerator: Restore power by plugging the refrigerator back in.
- Test the Refrigerator: Observe the refrigerator to ensure it is cooling properly and that frost is not accumulating.
Tips and Warnings
- Use Proper Tools: Ensure you use the correct tools to avoid damaging components.
- Handle with Care: When handling plastic components, warm them first to make them more pliable and avoid breakage.
- Consult the Manual: Always refer to your refrigerator’s user manual for specific instructions related to your model.
- Seek Professional Help: If you are unsure about any step or if the problem persists, consider seeking help from a professional technician.
By following these steps, you can effectively test the defrost thermostat in your refrigerator, ensuring it operates correctly and efficiently. Regular maintenance and timely repairs will help extend the lifespan of your appliance.
