Wine cooler displays F4 and may not defrost properly; frost accumulates on the evaporator and temperature rises.

Safety: Unplug the appliance before accessing the evaporator or control board. Avoid touching the heater until it has cooled.

Steps to address F4:

• Check for heavy frost: Remove shelves and inspect the rear interior panel. If it is heavily frosted, the defrost system is likely compromised.
• Access evaporator and defrost components: Remove the inner rear panel to expose the evaporator coil, defrost heater, and defrost sensor (thermistor or thermostat).
• Inspect defrost sensor: Locate the sensor clipped to the evaporator or attached to the tubing. Ensure it is firmly attached and not physically damaged. Check wiring for brittleness or breaks.
• Test defrost sensor: With power off, disconnect the sensor and measure resistance. Compare to the service chart for the approximate coil temperature. Replace if open, shorted, or out of range.
• Check defrost heater: Disconnect heater leads and measure resistance across the heater. A typical reading is a few tens of ohms. If it reads open (OL), the heater is failed and must be replaced.
• Inspect wiring and connectors: Verify continuity from the heater and sensor back to the main PCB. Repair any burnt or corroded connectors.
• Control board assessment: If heater and sensor test good but F4 persists and the unit never enters defrost, the defrost relay or control logic on the main PCB may be defective and require replacement.