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Whirlpool Freezer Not Defrosting/Ice Buildup

The part(s) or condition(s) listed below for the symptom Freezer not Defrosting/Ice Buildup are ordered from most likely to least likely to occur. Check or test each item, starting with the items at the top of the page.

Most Frequent Causes for Freezer not Defrosting/Ice Buildup

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Cause 1Defrost Thermostat

The defrost thermostat monitors the temperature of the evaporator coils. When the coils drop below a set temperature, the thermostat contacts close to allow power to flow to the defrost heater during the defrost cycle. In the defrost cycle, the defrost heater melts away any frost that may have accumulated on the evaporator coils. If the defrost thermostat is defective, the thermostat contacts will not close. As a result, the thermostat won’t provide power to the defrost heater. To determine if the defrost thermostat is defective, use a multimeter to test it for continuity. If the defrost thermostat does not have continuity when it reaches the low temperature of its operating range, replace it.

Parts
Cause 2Defrost Control Board

The defrost control board determines how often to run the defrost cycle. If the board fails, the freezer will not go into the defrost cycle. Before replacing the defrost control board, first test the defrost heater and defrost thermostat. If the defrost heater and defrost thermostat are working properly, the defrost control board is likely defective.

Parts
Cause 3Defrost Timer

The defrost timer turns on the defrost heater several times throughout the day to melt any frost that may have accumulated on the evaporator coils. If the defrost timer is defective, it may not advance into the defrost cycle, or it may not send power to the defrost heater during the defrost cycle. To determine if the defrost timer is defective, slowly advance the dial into the defrost cycle. The compressor should turn off and the heater should turn on. If the timer does not send power to the defrost components or advance out of the defrost cycle within 30 minutes, the defrost timer is likely defective and should be replaced.

Parts
Cause 4Defrost Heater Assembly

In a self-defrosting freezer, the defrost heater assembly turns on several times throughout the day to melt away any frost that may have accumulated on the evaporator coils. If the defrost heater assembly is defective, the defrost system will not work, and frost will continue to accumulate on the evaporator coils. To determine if the defrost heater is defective, use a multimeter to test it for continuity. If the defrost heater does not have continuity, replace it.

Parts
Cause 5User Control and Display Board

On some models the user control and display board may also control the defrost system. Control boards are frequently misdiagnosed—before replacing the user control and display board, first test all of the defrost system components. If none of the defrost system components are defective, consider replacing the user control and display board.

Parts
Cause 6Control Board

The control board has relays that send power to the freezer components. If the control board is defective, it may stop sending voltage to the defrost system. Control boards are frequently misdiagnosed—before replacing the control, first test all of the defrost system components. If none of the defrost system components are defective, consider replacing the control board.

Parts
Cause 7Main Control Board

The main control board regulates the power supplied to all of the freezer components, including the defrost system. If the main control board is defective, it may stop sending voltage to the defrost system. Control boards are frequently misdiagnosed—before replacing the main control, first test all of the defrost system components. If none of the defrost system components are defective, consider replacing the main control board.

Parts
Cause 8Manual Defrost

Chest freezers and some upright freezers with the evaporator tubing in the shelves are manual defrost. This means you will have to unplug or turn off the freezer for a period of time to clear the frost/ice. If the accumulation is 1/4" to 1/2" thick, the freezer will need to be defrosted.

Cause 9Freezer door left open

If there is a lot of frost accumulation on the food and around the door opening, it is likely the door was not closed properly for a lengthy period.

Cause 10Door Gasket

If the door gasket is not sealing properly, ice can form where the leak is. Inspect the door gasket for kinks or twists. You can use a hair dryer to try smoothing out the kinks. If the door gasket is damaged it will need to be replaced.

Parts