A mechanical defrost timer controls the defrost cycle of the freezer. If the timer malfunctions, it can cause the refrigerator to either stay in cooling mode or defrost mode, resulting in cooling issues or frost buildup.
Here’s a step-by-step guide to test the defrost timer.
Caution: Please read our safety information before attempting any testing or repairs.
Important Safety Notice: Before testing the defrost timer, unplug the refrigerator to avoid an electrical shock hazard.
Tools and Materials Needed
- Screwdriver (Phillips and flat-head)
- Needle-nose pliers
- Multimeter
- Safety gloves
Steps to Test the Defrost Timer
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: Locate the Defrost Timer
- Common Locations: The defrost timer is usually found behind the front grill (“toe kick”) of the refrigerator. It may also be found behind a cover plate inside the refrigerator or freezer, in the temperature control console, or behind the refrigerator near the compressor.
Step 3: Manually Advance the Timer
- Find the Advance Screw: Locate the advance screw on the defrost timer.
- Advance the Timer: Turn the advance screw clockwise until you hear it click. This will advance the timer to the next mode (from cooling to defrost mode or vice versa).
- Wait and Observe: Wait about 35 minutes and check if the timer advances out of the defrost mode back to cooling mode (listen for the compressor to turn on). If the timer does not advance, the timer motor is likely bad and needs to be replaced.
Step 4: Remove the Timer
- Remove Screws: The timer is usually held in place with one or more screws. Use a screwdriver to remove the screws.
- Disconnect Wiring Connector: Gently pull the timer out far enough to disconnect the wiring connector. Firmly pull and rock the connector left and right to remove it. The connector plug is keyed to fit only one way, so no need to note the wire positions.
Step 5: Test the Timer with a Multimeter
- Set the Multimeter: Set the multimeter to the ohms setting (Ω) on the X1 scale.
- Identify Terminals: The timer has four terminals. Locate the common terminal, usually labeled “3” or “C.” If the terminals are not labeled, identify the terminal with the white wire in the connector plug.
Step 6: Test for Continuity
- Initial Test:
- Touch one probe to the common terminal.
- Touch the other probe to each of the remaining three terminals.
- The multimeter should display a reading of zero or near zero ohms (continuity) for one or two pairs of terminals. One pair should show no continuity (infinity).
- Advance Timer and Retest:
- Locate the timer switch and turn it clockwise until you hear it click.
- Retest the timer as you did above.
- After advancing, one or two pairs of terminals should show continuity, and at least one pair should show infinity. One of the pairs that initially showed continuity should now read infinity, and one pair that read infinity should now show continuity.
Step 7: Interpret the Results
- Normal Operation:
- Continuity in one or two pairs of terminals initially.
- After advancing the timer, a different pair of terminals should show continuity while others show infinity.
- Faulty Timer:
- If the timer does not pass these tests (no change in continuity after advancing), it is likely defective and should be replaced.
*Note: Some models may have unique configurations. Refer to the refrigerator’s schematic or manual for specific details.
Step 8: Reassemble the Timer
- Reconnect the Wiring Connector: Plug the connector back into the timer.
- Secure the Timer: Reattach the timer with screws.
- Replace Access Panel: Secure any panels removed to access the timer.
Step 9: 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 operates correctly and cycles between cooling and defrosting.
Tips and Warnings
- Use Proper Tools: Ensure you use the correct tools to avoid damaging components.
- Handle with Care: Be gentle when handling connectors and terminals to avoid damage.
- 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 timer in your refrigerator, ensuring it operates correctly and efficiently. Regular maintenance and timely repairs will help extend the lifespan of your appliance.
