Sub-Zero Freezer Evaporator Frost Block / Airflow Loss

Freezer cold but refrigerator and ice maker both warm; ice production has stopped.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Defrost heater failure on freezer evaporator, Defective defrost bi‑metal, Failed freezer evaporator fan motor, Door gasket leak causing heavy frost

How to Fix / Troubleshooting

Safety first: Unplug the refrigerator before removing panels. Do not chip ice with sharp tools; you can puncture refrigerant lines.

Step 1 – Inspect for frost buildup

  • Look at the back wall of the freezer for heavy frost or ice bulging.
  • If the evaporator cover is frosted solid, air cannot circulate to the refrigerator or ice maker.

Step 2 – Perform a manual defrost

  • Remove food from the freezer and store in a cooler.
  • Unplug the unit and leave the freezer door open for 12–24 hours to melt all ice.
  • Clean up water and ensure the drain is clear.

Step 3 – Test defrost components

  • Access the freezer evaporator and locate the defrost heater and defrost bi‑metal.
  • Use a multimeter to check continuity of both parts; replace any that test open when they should be closed.

Step 4 – Check evaporator fan and gasket

  • Verify the freezer evaporator fan runs when the door switch is held closed.
  • Inspect the freezer door gasket for gaps, tears, or warping that could allow moist air in; replace if needed.
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Repair Difficulty

Hard 4/5

Required Part

Freezer Defrost Heater
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