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

Safety first: Unplug the refrigerator before any disassembly. Beware of sharp metal edges and hot components after recent operation.

Initial action:

• If there is heavy frost on the rear panel inside the freezer, perform a full manual defrost: unplug the unit, open doors, and allow all ice to melt. Place towels to catch water. Do not use knives or heat guns.

Component checks (for experienced DIYers):

• Access the evaporator: Remove drawers and the rear inner panel to expose the evaporator and defrost heater.
• Test the heater: Disconnect heater terminals and measure resistance. A typical heater will show a finite resistance (e.g., 50–300 Ω). Infinite resistance indicates an open heater that must be replaced.
• Check defrost thermostat/thermal fuse: With the evaporator cold (below freezing), the thermostat should read near 0 Ω. If it remains open, replace it.
• Inspect wiring: Look for burnt connectors, discolored insulation, or broken wires between heater, thermostat, and main PCB.

Reassembly and test: Replace any failed components, reassemble the panels, and restore power. Monitor for normal frost pattern and absence of E4 over several days.

Note: If heater and thermostat test good, the main control board's defrost relay or circuitry may be faulty and should be diagnosed and replaced by a professional.