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Refrigerator Defrost heater: What It Does and Signs It's Failing

A heating element under or wrapped through the freezer evaporator coil, behind the back panel or under the freezer floor. Several times a day it switches on briefly to melt the frost off the coil so air can flow through it.

How it works

The control (or an older defrost timer) cuts the compressor and powers the heater. A defrost thermostat or sensor ends the defrost once the coil is warm enough, and the meltwater runs down a drain to a pan under the fridge.

Signs it is failing

• A heavy, even layer of frost on the back panel of the freezer
• Fridge section warming while the freezer stays fairly cold
• Weak airflow from the vents
• Defrost codes
• Ice blocking the defrost drain

Defrost and 'defrost failed' codes point to the heater, the defrost thermostat or fuse, or the sensor. A clogged defrost drain can cause the same frosting.

Can you replace it yourself?

Unplug the fridge, empty the freezer and remove the back panel to see the coil. The heater comes off with a few clips and plugs, but it's slow work and the coil is easy to damage. Defrost the ice fully with the doors open; never use a knife or heat gun on the coil.

Buying the right part

Heaters come in glass-tube and metal-sheath styles with different lengths. Buy the exact OEM part for your model.

Error codes linked to the defrost heater

• dEDefrost system not working properlyGE
• Er FFFreezer fan is blocked or not runningLG
• Er dHDefrost cycle failedLG
• 21EFreezer fan is not turningSamsung
• 5EFridge defrost sensor errorSamsung
• F4E1Freezer defrost heater problemWhirlpool

Last reviewed 2026-10-19.