Display shows E4 and the wine cooler may shut down or fail to maintain set temperature.

Warning: Always disconnect power before accessing internal wiring or sensors.

To address E4:

• Check your model: Not all Koolatron wine coolers have a dedicated defrost sensor. On models that do, it is usually attached to the evaporator or near the compressor area.
• Access sensor: Remove the rear cover or interior rear panel as required by your model. Look for a small sensor clipped to tubing or the evaporator.
• Inspect for damage: Look for signs of overheating, melted insulation, or corrosion on the sensor and its wiring.
• Test continuity: Use a multimeter to check resistance. A blown thermal fuse-type sensor will read open (no continuity).
• Replace if open or shorted: Install a new Koolatron defrost/over-temperature sensor or thermal fuse assembly with the same rating. Secure it in the original location.
• Board evaluation: If the sensor tests normal but E4 persists, the main control board may be misreading the circuit and require replacement.