Display shows F5, freezer not defrosting properly, heavy ice buildup on evaporator, temperature gradually rises

Safety: Unplug the freezer before accessing the evaporator and electrical components. Beware of sharp fins and ice.

• Access evaporator area: Remove drawers and inner rear panel to expose the evaporator coil and defrost heater assembly.
• Inspect heater: Look for visible breaks, burn marks, or dislodged heater elements attached to the evaporator.
• Check continuity: Disconnect the heater leads and measure resistance with a multimeter. An open circuit indicates a failed heater that must be replaced.
• Check defrost thermostat / thermal fuse: Locate the thermostat or fuse clipped to the evaporator tubing. Test for continuity at freezer temperature (it should be closed). Replace if open.
• Inspect wiring: Follow the heater circuit wiring back to the harness and control board, checking for breaks or loose connectors.
• Replace faulty parts: Install a new Bauknecht-compatible defrost heater and/or thermostat as needed. Ensure proper positioning against the evaporator.
• Control board check: If all components test good but F5 persists, the defrost relay or triac on the main PCB may be defective. Board replacement is recommended via professional service.