Sub-Zero Condenser Heat Dissipation / Mullion Heater Overrun

Exterior cabinet sides or mullion strip between doors feel excessively hot to the touch.

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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

Dirty condenser coil, Failed condenser fan motor, High ambient temperature, Mullion heater stuck on due to control fault

How to Fix / Troubleshooting

Safety first: Unplug the unit before cleaning coils or accessing fans.

Step 1 – Clean condenser coil

  • Remove the grille and thoroughly vacuum the condenser coil.

Step 2 – Check condenser fan

  • Restore power and verify the condenser fan runs whenever the compressor is on.
  • Replace the condenser fan motor if it is not operating correctly.

Step 3 – Improve ventilation

  • Ensure adequate clearance around the unit and that warm air can escape from the grille area.

Step 4 – Control evaluation

  • If the mullion strip remains extremely hot even with a clean condenser and working fan, the mullion heater circuit or control board may be faulty and should be checked by a technician.
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Repair Difficulty

Medium 3/5

Required Part

Condenser Coil
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