Freezer displays E4 and may stop automatic defrosting, leading to heavy ice build-up on the evaporator.

Safety first: Unplug the freezer. Allow any ice to melt before working near the evaporator and heater to avoid damage and electrical hazards.

• Access evaporator and defrost components: Remove baskets and the rear inner panel to expose the evaporator coil, defrost heater, and defrost sensor.
• Inspect for heavy ice: If the evaporator is encased in ice, this confirms a defrost issue. Use towels and a tray to catch meltwater; do not chip ice with sharp tools.
• Check defrost sensor: Locate the defrost NTC (often clipped to the evaporator or near the heater). Disconnect and measure resistance at around 0–10°C (during defrost). Compare to expected NTC values. Replace the defrost NTC sensor if open or shorted.
• Test defrost heater: With the unit unplugged, disconnect the heater leads and measure resistance. A typical heater reads between 50–300 Ω. An open circuit indicates a failed defrost heater.
• Check thermal fuse/thermostat: If fitted, test continuity through the defrost thermal fuse or bimetal thermostat. Replace if open when cold.
• Reassemble and test: After replacing any faulty parts, fully defrost the evaporator, reassemble panels, and restore power. Monitor for normal defrost cycles over the next 24–48 hours and confirm that E4 does not return.

Note: If all components test good, the main control board’s defrost circuit may be defective and should be replaced by a technician.