Wine cooler beeps and displays E4; unit may not defrost properly or may ice up around the evaporator.

Safety warning: Disconnect power before working near the evaporator or heater. The defrost heater can be sharp and may have exposed metal edges.

Steps:

• 1. Inspect for heavy frost: Remove interior shelves and the rear interior panel. If the evaporator is encased in solid ice, the defrost system is likely not working.
• 2. Locate defrost sensor: The defrost thermistor is usually clipped to the evaporator tubing or mounted near the defrost heater. Check that it is firmly attached and not broken or corroded.
• 3. Test defrost sensor: With the unit unplugged, disconnect the sensor and measure resistance. Compare to expected NTC values. If the reading is open, shorted, or far off spec, replace the sensor.
• 4. Test defrost heater (if accessible): Disconnect heater leads and measure resistance with a multimeter. A typical small evaporator heater may read between 50–300 ohms. If it reads open (OL), the heater is failed and must be replaced.
• 5. Manual defrost: While waiting for parts, you can manually defrost by leaving the unit unplugged with the door open for several hours and placing towels to catch water. Do not use sharp tools to chip ice; this can puncture the evaporator.
• 6. Replace faulty components: Install a new defrost sensor and/or heater as needed, routing wires away from sharp edges and hot surfaces. Reconnect to the control board.
• 7. Reassemble and test: Reinstall panels, restore power, and monitor for E4. The unit should now defrost automatically and maintain clear airflow across the evaporator.

Note: If both sensor and heater test good, the main control board's defrost circuit may be defective and should be evaluated by a technician.