Display shows E4 and the refrigerator may not defrost properly, leading to ice buildup on the evaporator and poor cooling.

Safety warning: Unplug the IceKing refrigerator before testing the defrost heater or any live components.

Diagnostic procedure:

• 1. Visual inspection of freezer evaporator area: Remove freezer drawers and the rear inner panel to expose the evaporator and defrost heater (usually a metal or glass-encased element at the base or woven through the coil).
• 2. Check for obvious damage: Look for burnt spots, broken heater casing, or melted connectors. Inspect the defrost thermostat/thermal fuse (often clipped to the evaporator tubing) for signs of overheating.
• 3. Test the defrost heater: Disconnect the heater leads. Using a multimeter set to resistance, measure across the heater terminals. A typical reading is between 20–300 Ω depending on the model. Infinite resistance indicates an open heater that must be replaced.
• 4. Test the defrost thermostat/thermal fuse: At freezer temperature (below ~10°C), the thermostat should show continuity (near 0 Ω). If it is open at low temperature, replace it. Some models use a one-shot thermal fuse that must be replaced if open.
• 5. Inspect wiring and connectors: Check the harness from the heater and thermostat back to the main PCB for burns, corrosion, or loose pins. Repair or replace damaged connectors.
• 6. PCB evaluation: If heater and thermostat test good and wiring is intact, the main control PCB defrost relay or triac may have failed. This requires PCB replacement, best done by a qualified technician.

Note: After repairs, fully defrost any remaining ice, reassemble panels, and monitor operation for several days to confirm proper automatic defrosting.