Error code E4 appears and the refrigerator may stop cooling periodically or show signs of heavy frost on the evaporator.

Safety first: Unplug the appliance. Be cautious of sharp evaporator fins and electrical connectors.

How to proceed:

• 1. Access evaporator area: Empty the freezer, remove drawers, and unscrew the rear inner panel to expose the evaporator coil and wiring harness.
• 2. Identify defrost components: The defrost NTC sensor is usually clipped to the evaporator tubing; the defrost thermostat (if fitted) is a small round or oval device clamped to the coil with two wires.
• 3. Check for heavy ice: If the evaporator is a solid block of ice, allow it to defrost fully (doors open, towels in place, or use a hair dryer on low, keeping it away from plastic and wiring). Do not chip ice with sharp tools.
• 4. Test defrost thermostat: With the thermostat still cold (below freezing), disconnect its wires and measure continuity. It should read closed (near 0 Ω) when cold. If it remains open, replace it.
• 5. Test defrost NTC sensor: Disconnect the sensor and measure resistance. Compare to expected NTC values; open or shorted readings indicate failure.
• 6. Inspect connectors and harness: Reseat all plugs in the evaporator area and at the main PCB. Repair any damaged wires.
• 7. Replace faulty parts: Install a new defrost sensor and/or thermostat as needed, securing them in the original positions for accurate sensing.
• 8. Reassemble and test: Refit the evaporator cover, restore power, and monitor operation. If E4 returns with new sensors and good wiring, the main control board defrost circuit may be defective and should be replaced by a professional.