F21Serious
Miele Refrigerator F21 Error Code
The defrost heater is not working, causing frost buildup on evaporator.
Common causes
- Blown heater element
- Defrost thermostat failure
- Control board problem
How to fix it
- Check for frost on evaporator.
- Measure resistance of heater (should be ~50Ω).
- Inspect defrost thermostat continuity.
⚠ When to call a pro: If heater or thermostat tests bad.
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Always unplug the appliance (and turn off the water for washers/dishwashers) before inspecting. These guides are for information only and are not a substitute for a professional repair.