Wine cooler displays E4 and cooling stops or becomes erratic

Safety: Unplug the wine cooler. Allow any ice build-up to melt before working near the evaporator to avoid damage.

• Check for heavy ice: Remove interior rear panel and inspect the evaporator. If it is encased in ice, a defrost issue is likely.
• Locate defrost sensor: Often clipped to the evaporator tubing or embedded in foam near the top of the coil. It may be combined with the evaporator sensor on some Montpellier models.
• Test sensor and heater: With a multimeter, check resistance of the defrost sensor (should be in kΩ range) and continuity of the defrost heater (low ohms, not open). Refer to service data if available.
• Inspect wiring: Follow the heater and sensor wires back to the PCB. Look for burnt connectors, brittle insulation, or loose plugs.
• Temporary manual defrost: If the heater is faulty and you are waiting for parts, fully defrost the unit by unplugging and leaving the door open for 24 hours, protecting the floor from water. This will restore cooling temporarily.
• Replace failed components: Install a new defrost sensor or heater assembly compatible with your Montpellier model. Ensure good thermal contact between sensor and evaporator.
• PCB replacement: If all components test good but E4 persists, the main control board defrost circuit may be defective and should be replaced by a professional.