Freezer shows E4 and may stop automatic defrosting, leading to ice build-up on the evaporator.

Safety: Unplug the freezer before accessing the evaporator or defrost components. Surfaces may be sharp and may contain ice.

• Defrost the unit: If the evaporator is heavily iced, fully defrost the freezer by leaving it unplugged with doors open for several hours. Do not use sharp tools to chip ice.
• Access defrost components: Remove the internal rear panel to expose the evaporator coil. Locate the defrost thermostat (bi-metal) clipped to the evaporator and any additional defrost NTC sensor.
• Check wiring and connectors: Inspect for broken wires, burnt connectors, or signs of overheating around the thermostat and heater connections.
• Test the defrost thermostat: With the thermostat still cold (below its closing temperature, typically below 0 °C), disconnect it and measure continuity. It should read closed (near 0 Ω). Warm it gently in your hand; it should open (OL) when warm. If it stays open or closed, replace it.
• Test defrost NTC (if fitted): Measure resistance and compare to expected NTC values. An open or shorted reading indicates failure.
• Replace faulty parts: Install a new defrost thermostat and/or defrost sensor (NTC) as required, using Hoover-approved parts. Clip them securely to the evaporator in the original positions.
• Reassemble and test: Refit the evaporator cover, restore power, and monitor for normal defrost cycles over the next 24 hours. The E4 code should clear automatically on many models after a successful defrost cycle.

Technician advice: If sensors and thermostat are good but E4 persists, the main control board defrost circuit may be faulty and should be checked by a professional.