Wine cooler displays E4 and may not defrost properly; ice builds up on back wall

Safety: Unplug the appliance before working near the evaporator or electrical components. Melted ice can create slip and shock hazards.

Steps to address E4:

• Manual defrost: Open the door and unplug the cooler. Allow all ice on the back wall and evaporator to melt completely. Do not chip ice with sharp tools.
• Access evaporator and defrost components: Remove the internal rear panel to expose the evaporator coil, defrost heater, and defrost sensor.
• Locate defrost sensor: It is usually clipped to the evaporator tubing or attached with a metal clip and insulation. Verify it is firmly attached and not corroded.
• Test defrost sensor: Disconnect the sensor and measure resistance with a multimeter. At near-freezing temperatures, it should show a moderate resistance (often 10–30 kΩ). An open or short indicates failure.
• Check defrost heater: Identify the heater element (a metal tube or wire along the evaporator). Disconnect its leads and measure resistance; a typical heater will show a low but non-zero resistance (e.g., 50–300 Ω). An open circuit means the heater is faulty.
• Inspect wiring and PCB: Check for burnt connectors, melted insulation, or signs of overheating. On the main control PCB, inspect the defrost relay area for discoloration or cracking.
• Replace faulty parts: Replace the defrost NTC sensor if readings are incorrect. If the heater is open, replace the defrost heater element. If both test good but E4 persists, the main control PCB may need replacement.

Warning: Defrost heater circuits operate at mains voltage. If you are not experienced with electrical testing, seek professional service.