Wine cooler shows E4 and may not defrost properly, with ice buildup on the evaporator

Safety: Disconnect power and wear cut-resistant gloves when working around metal panels and sharp evaporator fins.

E4 is commonly associated with the defrost sensor or evaporator thermistor.

• Step 1 – Inspect for frost: Remove interior rear panel and check the evaporator. Heavy, solid ice buildup indicates a defrost system issue.
• Step 2 – Locate defrost sensor: The sensor is typically clipped to the evaporator tubing near the top or middle. Ensure it is firmly attached and not hanging loose.
• Step 3 – Check wiring: Look for broken or corroded wires near the evaporator where moisture is common. Reseat the connector at both the sensor and the control board.
• Step 4 – Test sensor: With the unit unplugged, disconnect the sensor and measure resistance. If the evaporator is iced, you should see a higher resistance than at room temperature. An open or shorted reading indicates a bad sensor.
• Step 5 – Replace sensor: Install a new defrost/evaporator thermistor, clipping it securely to the coil in the same location. Avoid bending the aluminum fins excessively.
• Step 6 – Board evaluation: If the sensor and wiring are good but E4 persists and defrost cycles do not occur, the main control board defrost circuit may be defective and should be replaced by a professional.