Display shows E4 and the refrigerator may not defrost, causing heavy frost on the evaporator and poor cooling.

Safety first: Unplug the refrigerator. The defrost heater operates at mains voltage; do not test it live unless you are qualified.

Visual inspection:

• Access the evaporator by removing the freezer rear panel.
• Look for burnt spots on the heater, melted insulation, or disconnected wires.
• Check the defrost thermostat/thermal fuse (usually clipped to the evaporator tubing) for signs of overheating or cracking.

Basic continuity checks (if you have a multimeter):

• With power off and wires disconnected, measure continuity across the heater terminals. An open circuit indicates a failed heater.
• Check continuity through the defrost thermostat/thermal fuse at freezer temperature; an open reading may indicate a blown safety device.

Temporary workaround: Manually defrost the unit by unplugging it and leaving doors open for 12–24 hours, placing towels to catch water. This will restore cooling temporarily until the defrost system is repaired.

Important: If you are not comfortable testing high-voltage components, contact a professional. Replacing the heater or control board incorrectly can cause fire or shock hazards.