Freezer shows E4 and may stop defrosting or ice builds up on evaporator

Safety: Unplug the freezer. Allow any heavy ice build-up to soften before working near the evaporator to avoid damaging coils.

• Access evaporator area: Remove baskets and inner rear panel to expose the evaporator, defrost heater, and defrost sensor.
• Check for heavy ice: If the evaporator is a solid block of ice, the defrost system is not working correctly. Manually defrost with towels and a bowl of hot (not boiling) water; never use sharp tools or heat guns.
• Inspect defrost sensor: Locate the defrost NTC (often clipped to the top of the evaporator). Check wiring and connector. Test resistance at freezer temperature and again at room temperature; it should change significantly. Replace if open/shorted or out of spec.
• Test defrost heater: Disconnect heater leads and measure resistance. A typical heater will show a finite resistance (e.g., 50–300 Ω). If it reads open circuit, replace the heater.
• Check thermal fuse/thermostat: If fitted, test continuity through the defrost thermal fuse or bimetal thermostat. Replace if open when at normal freezer temperature.
• Inspect PCB: If all components test good, the defrost relay or triac on the main control board may be faulty. Look for burn marks or a stuck relay.

Replacing the main control board or working on the defrost heater wiring should be done by a qualified technician if you are not experienced with appliance electrics.