Refrigerator shows E4 and there is excessive frost or ice on the freezer evaporator, with poor cooling in the fridge section.

Safety: Unplug the refrigerator before testing the heater or working near wiring.

• Access evaporator and heater: Remove freezer drawers and the rear interior panel. The defrost heater is usually a metal or glass-encased element at the bottom or woven through the evaporator.
• Check for heavy ice: If the evaporator is a solid block of ice, the defrost system is likely not working. Fully defrost the unit (doors open, towels on floor) for several hours.
• Test heater continuity: Disconnect the heater connectors and measure resistance with a multimeter. A typical heater will show low resistance (e.g., 20–200 Ω). Infinite resistance indicates a failed heater.
• Inspect thermal fuse/bimetal: Locate the defrost thermostat or thermal fuse clipped to the evaporator tubing. Test for continuity at freezing temperatures; an open reading at cold temperature indicates failure.
• Replace faulty components: Install a Cecotec-compatible defrost heater and/or defrost thermostat/thermal fuse as needed. Ensure all connections are tight and properly insulated.
• Control board check: If heater and thermostat test good but E4 persists, the main control board defrost circuit may be defective and require replacement by a qualified technician.