Wine cooler shows E4 and may stop cooling or enter a protection mode; compressor may not start.

Safety warning: Disconnect power before accessing the evaporator or control board. The defrost heater and wiring can be live when powered.

Procedure:

• 1. Access evaporator compartment: Remove internal shelves and the rear inner panel to expose the evaporator coil and defrost components.
• 2. Identify defrost sensor: On La Sommeliere units with automatic defrost, a dedicated NTC may be clipped to the evaporator or embedded in the defrost harness. Verify its position and attachment.
• 3. Check for heavy ice buildup: If the evaporator is encased in ice, the defrost system may have failed. Manually defrost by leaving the unit unplugged with doors open and towels to catch water for 12–24 hours.
• 4. Test defrost sensor: Measure resistance at room temperature and again when cooled (e.g., in ice water). The resistance should change smoothly. Open or shorted readings indicate a bad sensor.
• 5. Inspect defrost heater: If accessible, check continuity of the defrost heater element with a multimeter. An open circuit means the heater is faulty.
• 6. Check wiring and PCB: Inspect connectors from the defrost sensor and heater to the main control board. Look for burnt spots or damaged tracks on the PCB near the defrost relay.
• 7. Replace faulty parts: Install a new La Sommeliere defrost NTC sensor or defrost heater as needed. Ensure proper mounting and insulation.
• 8. Reassemble and test: After reassembly, restore power and monitor for recurrence of E4 and for normal frost patterns on the evaporator.

Note: If you are not comfortable testing live defrost circuits or relays, contact a professional technician.