Wine cooler beeps and shows E4; compressor or fans may not start or may shut off quickly.

Safety warning: Unplug the unit before servicing. The defrost circuit involves line voltage components that can cause electric shock.

Steps to troubleshoot E4:

• Power reset: Disconnect power for 10 minutes and reconnect. If E4 returns, continue.
• Access evaporator area: Remove interior shelves and the rear interior panel to expose the evaporator coil, defrost heater, and defrost sensor.
• Locate the defrost sensor: It is often clipped to the evaporator tubing or mounted near the top of the evaporator, separate from the main evaporator thermistor.
• Inspect for ice buildup: Heavy ice accumulation around the evaporator and sensor can cause incorrect readings. Fully defrost the unit by leaving it unplugged with the door open for several hours.
• Check wiring and connectors: Inspect the defrost sensor and heater wiring for burns, breaks, or loose connections. Verify that connectors at the sensor and control board are firmly seated.
• Test the defrost sensor: With the unit unplugged, disconnect the defrost sensor and measure its resistance at room temperature. Compare to NewAir’s specifications. An open or shorted sensor must be replaced.
• Test the defrost heater (if accessible): Disconnect the heater leads and measure resistance. A typical heater will show a finite resistance (often 50–300 Ω). An open circuit indicates a failed heater.
• Replace faulty parts: Install a new NewAir defrost sensor and/or NewAir defrost heater as needed. Mount the sensor in the same location on the evaporator tubing and secure wiring away from sharp edges.
• Reassemble and test: Reinstall the interior panel, restore power, and monitor for several cooling cycles to ensure E4 does not return.

Note: If sensors and heater test good, the main control board’s defrost circuit may be defective and should be replaced by a professional.