If your Whirlpool, KitchenAid, or Maytag bottom-mount refrigerator is not cooling properly, a faulty defrost thermostat may be the cause. This part connects to the evaporator and helps control the defrost cycle. When it fails, frost can build up and make it harder for the refrigerator to stay at the right temperature. Replacing the defrost thermostat can help return the appliance to normal cooling.
Here are the steps to follow if you plan to do the replacement yourself.
How the Defrost Thermostat Works
Understanding the role of the thermostat will help you diagnose problems more easily. Here’s what this part does:
- Senses the temperature of the evaporator coils during cooling cycles
- Interrupts power to the defrost heater when the coils reach a certain temperature
- Allows the defrost heater to turn back on when frost levels return
- Helps keep the evaporator clear of excess ice, so airflow is not blocked
- Supports cycling between cooling and defrost modes to maintain stable operation
A failed thermostat may stay open or closed, disrupting the balance between cooling and defrosting and leading to rising temperatures or frost buildup.
Signs the Defrost Thermostat Might Be Faulty
Knowing when to replace this part can help prevent larger cooling problems. Here are signs that may indicate a faulty defrost thermostat:
- Ice buildup on the evaporator coils
- Refrigerator feels warm even when the freezer is cold
- Excess frost inside the freezer
- Frequent or prolonged defrost cycles
- Refrigerator runs continuously without cycling off
- Unusual clicking sounds from the freezer area
If you notice one or more of these symptoms, it may be time to check or replace the thermostat.
Tools and Materials
Before starting the repair, gather these tools and supplies:
- Flat head screwdriver
- 1/4 inch nut driver
- Wire cutters
- Wire strippers
- Wire crimpers
- Heat shrink tubing
- Heat gun or hair dryer
- Defrost thermostat (part number WP67006387)
- Insulated gloves and safety glasses
Safety Precautions
Working with appliances requires attention to safety. Prepare your space and protect yourself by following these reminders:
- Disconnect the refrigerator from power. Either unplug it or switch off the circuit breaker.
- Do not work in wet conditions or with wet hands. Make sure the area is completely dry.
- Clear the workspace of clutter. Remove anything that could cause you to trip or lose balance.
- Work in a well-lit area so you can clearly see what you are doing.
- Keep children and pets away from the space while repairs are being done.
- Use insulated gloves to protect your hands from sharp metal parts or electrical wires.
- Wear safety glasses to protect your eyes while cutting wires or using heat tools.
- Check your refrigerator’s user manual for details about your model or part location.
How to Replace the Defrost Thermostat on a Refrigerator
Follow these steps to access, remove, and replace the defrost thermostat safely and correctly.
Accessing the Thermostat
- Unplug the refrigerator or switch off its circuit breaker.
- Open both the refrigerator and freezer doors.
- Remove all shelves and storage bins from the compartments.
- Locate the freezer door screws—two at the top back and one at the bottom.
- Use a Phillips screwdriver to loosen the top screws.
- Remove the bottom screw completely.
- Lift the freezer door off and set it aside.
- Push the freezer door rails inward to gain access to the back panel screws.
- Use a flat-head screwdriver to pop off the plastic covers hiding the back panel screws.
- Remove the thermistor from its holder.
- Use a 1/4-inch nut driver to remove the four screws securing the evaporator panel.
- Gently pull the back panel out while avoiding any wires or cooling lines.
- Locate the defrost thermostat clipped onto a copper refrigerant tube in the back right area of the freezer.
Replacing the Thermostat
- Unclip the old thermostat from the copper tubing.
- Be careful around the evaporator fins, which can be sharp.
- Use wire cutters to cut the wires connected to the thermostat close to its body.
- If needed, use wire strippers to remove about 1/4 inch of insulation from each wire end.
- Slide heat shrink tubing onto each wire.
- Use wire crimp connectors to join the thermostat wires to the refrigerator wires.
- Slide the heat shrink tubing over the connectors and apply heat to seal the connections.
- Clip the new thermostat onto the copper tubing in the same position as the original.
- Arrange the wires neatly to keep them away from coils, fins, and the fan.
Reassembling and Testing
- Reposition the back panel, aligning sensor wires or probes in their slots.
- Reinstall and tighten the four screws using a 1/4-inch nut driver.
- Reattach the thermistor to its holder on the back panel.
- Replace the plastic screw covers.
- Set the freezer door back on its upper mounting points.
- Reinsert and tighten the top and bottom screws to secure the door.
- Put all shelves and bins back in their original places.
- Plug the refrigerator back in or turn the circuit breaker on.
- Let the appliance run for 15 to 30 minutes.
- Check that both the refrigerator and freezer sections are cooling properly.
- If cooling does not resume, check the wiring connections to the new thermostat.
Also Read: DIY Guide: How to Replace a Refrigerator Defrost Bi-Metal Thermostat
To Recap
Swapping out the defrost thermostat in your refrigerator might seem a bit technical, but it’s a job many people can do with basic tools and some patience. Understanding what this part does and knowing the warning signs can help you fix the problem before it gets worse. If you’ve noticed frost building up or the fridge section warming up, changing this small part could help bring things back to normal.
Follow the steps carefully, double-check your connections, and give your fridge time to cool down afterward. This repair is a smart way to get things working again without needing to wait for a technician.