Wine cooler beeps and displays E4; the unit may stop cooling or run erratically.

Safety: Unplug the wine cooler. Allow any ice to melt before working near the evaporator and heater.

• Access evaporator and defrost components: Remove interior shelves and the rear inner panel to expose the evaporator coil, defrost heater, and defrost sensor.
• Inspect for heavy frost: Excessive ice buildup indicates a defrost failure. Note the condition before proceeding with defrosting.
• Test defrost sensor: Disconnect the defrost sensor and measure its resistance with a multimeter. Compare the reading to NTC specifications. Replace if open, shorted, or out of range.
• Test defrost heater: Disconnect the heater leads and measure resistance. A typical heater will show a finite resistance (e.g., 50–300 Ω). If open (OL), replace the defrost heater.
• Check wiring and connectors: Inspect the wiring harnesses from the evaporator area to the main PCB for damage or corrosion. Repair or replace as needed.
• Control board: If the sensor and heater test good, the defrost relay or control circuit on the main PCB may be faulty. Replacement of the main PCB is recommended and should be performed by a qualified technician.