Display shows E5 and the unit runs continuously or not at all; temperature overshoots setpoint.

Safety warning: Unplug the wine cooler before accessing the evaporator or control board. The defrost heater operates at mains voltage.

Procedure:

• Inspect evaporator: Remove the interior rear panel. If the evaporator is encased in ice, the defrost system is likely not working.
• Check defrost sensor: Locate the small sensor clipped to the evaporator tubing. Disconnect and measure resistance; compare to other NTC sensors. An open or shorted reading indicates failure.
• Test defrost heater: With the unit unplugged, disconnect the heater leads and measure resistance. A typical heater will show a finite resistance (e.g., 50–300 Ω). Infinite resistance means the heater is open and must be replaced.
• Inspect wiring and connectors: Look for burnt connectors or broken wires between the heater, sensor, and main PCB.
• Replace faulty parts: Install a new defrost heater or defrost NTC sensor as needed, ensuring good thermal contact with the evaporator.
• Reassemble and test: Refit panels, restore power, and monitor operation over 24 hours to ensure normal frost pattern and that E5 does not return.

Warning: If the control board’s defrost driver is damaged, board replacement is typically required and should be done by a qualified technician.