Wine cooler displays E4 and may shut down cooling or run continuously; defrost may not operate correctly on compressor models.

Safety: Disconnect power before accessing the evaporator compartment or control board. Components may have sharp edges and may be wet from defrost.

Steps:

• Inspect evaporator area: Remove the interior rear panel and check for heavy ice buildup on the evaporator. Excessive ice suggests a defrost failure.
• Check defrost sensor: Locate the defrost sensor (often an NTC clipped to the evaporator tubing). Disconnect and measure resistance. Compare to expected values at the current temperature. Replace if open, shorted, or physically damaged.
• Test defrost heater (if equipped): On compressor-based Dometic wine coolers with automatic defrost, measure resistance of the defrost heater. An open circuit indicates a failed heater that must be replaced.
• Inspect wiring: Trace the defrost sensor and heater wiring back to the main control PCB. Repair any burnt, loose, or corroded connectors.
• Control board check: If sensor and heater are good, the main control PCB defrost relay or circuitry may be faulty. Replace the board if no other issues are found.