Wine cooler displays E4 and may shut down cooling or run erratically.

Safety first: Unplug the wine cooler before accessing the evaporator or any wiring. The defrost heater and related wiring can be sharp and may have exposed metal edges nearby.

Steps to troubleshoot:

• 1. Check for heavy frost buildup: Remove interior shelves and the rear evaporator cover. If the evaporator coil is encased in solid ice, the defrost system is likely not operating.
• 2. Manually defrost: With power disconnected, allow the unit to sit with the door open until all ice melts. Use towels to catch water; do not use sharp tools to chip ice.
• 3. Inspect defrost heater: The heater is typically a metal or glass-encased element at the base or woven through the evaporator. Look for breaks, burn marks, or discoloration.
• 4. Test heater continuity: Disconnect heater leads and measure resistance with a multimeter. A good heater will show finite resistance (often 20–200 Ω). Replace if open.
• 5. Check defrost thermostat/thermal fuse: Locate the thermostat clipped to the evaporator tubing. Test for continuity when the thermostat is cold (surrounded by ice or chilled). Replace if it remains open when cold.
• 6. Inspect wiring and connectors: Look for burnt connectors or brittle wires in the defrost circuit. Repair or replace damaged wiring using high‑temperature rated wire.
• 7. Control board evaluation: If heater and thermostat test good, the main control board may not be energizing the heater. This typically requires board replacement by a professional.

Note: After replacing any defrost component, clear the error by disconnecting power for several minutes, then monitor for normal frost pattern and absence of E4.