Display shows E4 and the refrigerator shows signs of defrost problems (ice buildup on back wall, poor cooling).

Safety first: Unplug the refrigerator. The defrost heater operates at mains voltage and can be dangerous.

Steps:

• Access the evaporator and heater: Remove freezer drawers and the rear inner panel to expose the evaporator coil. The defrost heater is usually a metal or glass-encased element at the bottom or woven through the evaporator.
• Visual inspection: Look for burnt spots, broken heater tubes, or disconnected wires at the heater terminals.
• Continuity test: Disconnect the heater wires and measure resistance across the heater terminals. A typical heater will show low resistance (10–200 Ω depending on design). Infinite resistance indicates an open heater.
• Check wiring and connectors: Inspect the harness from the heater to the main control PCB for burns, melted insulation, or loose connectors. Repair or replace damaged wiring.
• Replace heater if open: Install a new Etna defrost heater element compatible with your model. Ensure it is properly clipped to the evaporator and that all connections are tight.
• Reassemble and test: Refit the rear panel, restore power, and allow the unit to run through a defrost cycle. The E4 code should clear if the circuit is restored.