Freezer displays E3 and may not defrost properly, leading to ice buildup on the rear wall.

Safety first: Disconnect mains power before accessing the evaporator or heater. Risk of electric shock and sharp metal edges.

How to proceed:

• 1. Manually defrost: Empty the freezer, unplug it, and leave the door open for 24 hours with towels to catch meltwater. This will temporarily restore cooling if the issue is defrost-related.
• 2. Access the evaporator area: Remove drawers and the inner rear panel to expose the evaporator coil, defrost heater, and defrost sensor.
• 3. Inspect components: Look for burnt or broken sections of the defrost heater, loose connectors, or a blown thermal fuse/defrost thermostat clipped to the evaporator tubing.
• 4. Test the defrost heater: With the appliance unplugged, disconnect the heater leads and measure resistance. A typical heater will show a finite resistance (often 50–300 Ω). An open circuit indicates a failed heater.
• 5. Test the defrost sensor/thermostat: Measure resistance across the defrost sensor or thermostat. A defrost thermostat may be closed (low resistance) when cold and open when warm. An NTC sensor should show kΩ-level resistance that changes with temperature.
• 6. Replace faulty parts: If the heater is open, replace it with a Neff-compatible defrost heater assembly. If the thermal fuse or thermostat is open, replace it as a set with the heater if supplied that way. Ensure all clips and insulation are reinstalled correctly.
• 7. Control module check: If all defrost components test good, the main control module may not be energizing the heater. This requires live testing and is best left to a qualified technician.