Display shows E4 and the refrigerator may not defrost, or may over-defrost causing temperature swings.

Safety: Unplug the refrigerator. The defrost heater operates at mains voltage; do not test it live.

• 1. Access the evaporator area: Remove freezer drawers and the rear interior panel to expose the evaporator and defrost heater assembly.
• 2. Visual inspection: Look for burnt spots on the heater, melted connectors, or a tripped/bulged thermal fuse or bimetal thermostat attached to the evaporator tubing.
• 3. Test the heater: Disconnect the heater leads and measure resistance with a multimeter. A typical heater will show low resistance (e.g., 20–150 Ω). If it reads open (OL), replace the heater.
• 4. Test the defrost thermostat/fuse: At freezer temperature, the defrost thermostat should be closed (low resistance). If it is open at freezing temperatures, it is likely faulty. Thermal fuses should always show continuity; if open, replace.
• 5. Inspect wiring and connectors: Repair any burnt or loose connectors. Ensure good contact at the main harness.
• 6. If components test good: The main PCB defrost relay or control logic may be defective. Board replacement is typically required and is best done by a professional.

Note: After repair, fully defrost the evaporator before restarting to avoid immediate re-icing.