Wine cooler displays E4 and may stop cooling or run erratically; defrost may not function correctly.

Safety: Disconnect power before servicing. Components around the evaporator and heater can have sharp edges.

• Access evaporator area: Remove interior shelves and the rear panel to expose the evaporator and defrost components.
• Locate defrost sensor: The defrost thermistor is usually clipped to the evaporator tubing or near the defrost heater. Inspect for ice encasement, broken wires, or loose clips.
• Check for heavy frost: If the evaporator is a solid block of ice, manually defrost the unit (power off, doors open) until all ice is gone. This may temporarily restore operation but does not fix the underlying issue.
• Test defrost thermistor: Disconnect the thermistor and measure resistance at known temperatures (e.g., in ice water ~32°F / 0°C). Compare to the manufacturer’s NTC chart if available. Replace if readings are out of spec.
• Test defrost heater: With the unit unplugged, disconnect heater leads and measure resistance. A typical heater will show a finite resistance (often 50–300 ohms). If open (OL), the heater is bad and must be replaced.
• Inspect wiring and board: Check wiring from heater and sensor back to the main control board. Look for burnt connectors or signs of overheating at the defrost relay. If the relay is damaged or not energizing (requires live testing by a qualified person), replace the main control board.

Because defrost circuits involve mains voltage, consider using a professional technician if you are not experienced with electrical testing.