Main electrical panel beside a subpanel with its cover removed

Field pattern: frost-free upright freezer warming up with frost on the back panel (defrost failure, not refrigerant)

When the defrost system stops working, frost grows on the evaporator until the fan cannot move air and the cabinet warms even though the compressor runs. It looks like low refrigerant but is usually a defrost heater, defrost thermostat (bimetal), timer or control. Look at the coil before thawing it and test the defrost parts.

Cross-checked ~60 min moderateBrands: All

Before you start

Unplug before removing the evaporator cover
Do not chip ice off the evaporator; tubing punctures are sealed-system repairs
Live checks on the timer or board are caution

Diagnostic steps

Unlock all 7 steps with expected values

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