How automatic defrost works
Every frost-free refrigerator has an evaporator coil hidden behind a panel in the freezer (and on some models, a second one in the fresh-food section). Moisture from the air freezes onto that coil. Several times a day the control switches the compressor off and turns on a defrost heater. A defrost thermostat or sensor watches the coil temperature and ends the cycle when the frost is gone. The water runs down a drain to a pan near the compressor and evaporates.
If any one of those parts fails, frost keeps building until the coil is a solid block of ice.
Signs of a defrost failure
- Fresh-food section warm, freezer still cold, getting worse over several days
- Heavy, even frost on the back panel of the freezer
- Grinding or ticking noise as the fan blade hits ice
- Water inside the refrigerator or ice on the freezer floor from a frozen drain
- Cooling returns for a while after the refrigerator is unplugged, then fails again
What we repair
| Part | What it does | Common failure |
|---|---|---|
| Defrost heater | Melts frost off the evaporator | Burns open; no heat |
| Defrost thermostat (bimetal) | Ends the cycle when the coil warms | Fails open; heater never runs |
| Defrost / evaporator sensor | Reports coil temperature to the board | Reads wrong; defrost too short or never starts |
| Defrost timer or main control | Starts the defrost cycle | Timer stuck; relay on board fails |
| Drain heater and drain tube | Keeps the drain clear | Frozen drain, water leaks |
Defrost repair usually costs $220 to $380 on standard refrigerators and $350 to $600 on built-ins, including the part. See pricing.
Frequently asked questions
Can I fix it by manually defrosting the refrigerator?
Unplugging the refrigerator for 24 to 48 hours melts the ice and restores cooling for a while, but the failed part is still there. The frost returns, usually within one to three weeks.
Is a defrost problem expensive?
No. It is one of the most common and least expensive cooling repairs. A refrigerator that "stopped cooling" is far more often a defrost failure than a bad compressor.