Display shows E4 and unit may not defrost properly or may ice up around the evaporator.

Safety: Disconnect power before accessing internal components. Beware of sharp metal edges around the evaporator.

• Inspect evaporator area: Remove interior shelves and the evaporator cover. Look for a separate sensor or thermostat clipped to the evaporator coil (sometimes combined with the evaporator thermistor).
• Check for heavy ice: If the evaporator is a solid block of ice, allow a full manual defrost (door open, towels) until all ice is gone. After defrosting, restore power and see if E4 returns.
• Test defrost sensor: Disconnect the defrost sensor and measure resistance. Compare to expected NTC values; open or short readings indicate failure.
• Check defrost heater (if present): On compressor-based Antarctic Star models with heaters, locate the heater element at the base or around the evaporator. Test continuity with a multimeter; no continuity means the heater is open and must be replaced.
• Inspect wiring and connectors: Trace the defrost sensor and heater wires back to the main control PCB. Ensure all connectors are tight and wires are not burnt or broken.
• Replace faulty parts: Install a new defrost sensor / thermistor or defrost heater as needed. Reassemble the evaporator cover carefully to avoid air leaks.
• Control board replacement: If sensors and heater test good, the main control PCB defrost circuit may be defective and require replacement.