Wine cooler displays E4 and may stop cooling or run erratically.

Safety Warning: Unplug the unit before accessing the evaporator or control board. The defrost heater operates at line voltage and can cause shock.

Procedure:

• Check for heavy frost: Remove interior panels and inspect the evaporator. A solid block of ice indicates a defrost problem.
• Locate defrost thermistor: It is typically clipped to the evaporator tubing near the center or top of the coil.
• Test defrost thermistor: With the unit unplugged, disconnect the thermistor and measure resistance. If the coil is frosty, the resistance should be higher than at room temperature but not open or shorted. Replace if readings are abnormal.
• Test defrost heater: Disconnect heater leads and measure resistance across the heater. A typical reading is between 20–200 ohms depending on design. An open circuit indicates a failed heater.
• Inspect wiring and connectors: Look for burnt connectors or brittle wires near the heater and thermistor.
• Control board check: If both heater and thermistor test good, the defrost relay or control logic on the main control board may be faulty. Inspect for burnt spots and replace the board if necessary.
• Manual defrost (temporary fix): If the evaporator is iced over, you can unplug the unit, leave the door open, and allow it to fully defrost (use towels to catch water). This may restore cooling temporarily but does not fix the underlying issue.

Note: Avoid using sharp tools to remove ice; this can puncture the evaporator and cause irreparable damage.