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HomeRepair HelpThermador Refrigerator RepairThermador Refrigerator has frost or ice buildup Repair
Thermador Refrigerator has frost or ice buildup
If your Thermador is building frost or ice, the fridge is failing to clear its defrost cycle and ice is forming on the evaporator or in the drain. The most likely causes, in order, are a failed defrost control board (test the defrost heater and thermostat first), a faulty defrost timer that won’t advance or send power to the heater, a stuck water inlet valve that can cause an ice maker to overflow, a failing evaporator fan motor that lets cold air migrate and freeze the drain, and a missing or damaged drain strap that helps melt ice in the defrost drain. A clogged defrost drain or a refrigerator not defrosting properly often shows the same buildup, so check the drain and drain strap while you test the heater, thermostat, timer and fan. If a part is bad, you can enter your model number on RepairClinic.com to find the exact replacement part for your refrigerator and get step-by-step repair guidance.
01 - Thermador Refrigerator Defrost Control Board
The defrost control board determines how often to run the defrost cycle. If the board fails, the refrigerator 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.
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02 - Thermador Refrigerator Defrost 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, this indicates that the defrost timer is not advancing. If ...
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03 - Thermador Refrigerator Water Inlet Valve
The water inlet valve requires a minimum of 20 psi to shut off properly. If the water pressure is too low, the valve may not close fully once the power is shut off. As a result, the valve will leak water into the ice maker and cause the ice maker to overflow. Check the water pressure to determine if it is at least 20 psi. If the water pressure is sufficient, the water inlet valve is likely defective. The valve may not shut off all the way or may be stuck open, causing water to leak through the valve. If the water pressure is sufficient, but the ice maker is still overflowing, replace the water inlet valve.
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04 - Thermador Refrigerator Fan Motor
If the refrigerator's defrost drain is clogged, it's possible the evaporator fan motor is not working. If the evaporator fan is not running, cold air from the evaporator can migrate to the defrost drain causing ice buildup in the drain. To determine if the evaporator fan motor is defective, try turning the fan blade by hand. If the fan blade does not turn freely, replace the fan motor. Additionally, if the motor is unusually noisy, replace it. Finally, if the motor does not run at all, use a multimeter to test the motor windings for continuity. If the windings do not have continuity, replace the evaporator fan motor.
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05 - Thermador Refrigerator Drain Strap
Some defrost drains are outfitted with a drain strap. The drain strap is a small piece of copper or aluminum that attaches to the defrost heater and extends partway into the defrost drain. When the defrost heater turns on, heat is conducted through the drain strap to melt away any ice that may have accumulated further down in the defrost drain. If the drain strap is not in place, the defrost drain may be more likely to freeze over.
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06 - Thermador Refrigerator Evaporator Fan Motor
If the refrigerator's defrost drain is clogged, it's possible the evaporator fan motor is not working. If the evaporator fan is not running, cold air from the evaporator can migrate to the defrost drain causing ice buildup in the drain. To determine if the evaporator fan motor is defective, try turning the fan blade by hand. If the fan blade does not turn freely, replace the fan motor. Additionally, if the motor is unusually noisy, replace it. Finally, if the motor does not run at all, use a multimeter to test the motor windings for continuity. If the windings do not have continuity, replace the evaporator fan motor.
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Frequently Asked Questions
My refrigerator is not defrosting and has ice buildup — what should I check?
Fridge not cooling but freezer works — could frost buildup cause that?
How can I tell if the defrost drain is clogged and where is the defrost drain located?
Why is my ice maker overflowing with water?
How do I enter my model number on RepairClinic.com to find the correct replacement part?
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