Display shows E4 and the freezer ices up or the unit struggles to maintain temperature.

Safety warning: Always disconnect mains power before accessing the rear or internal panels. The defrost heater operates at mains voltage.

Procedure:

• 1. Confirm symptoms: Look for thick ice on the freezer evaporator cover and poor cooling performance.
• 2. Access the evaporator and heater: Remove freezer drawers and the rear internal panel. The defrost heater is usually a metal or glass-encased element fixed to the bottom or around the perimeter of the evaporator.
• 3. Visual inspection: Check for burnt spots on the heater, melted connectors, or discolored wiring.
• 4. Test continuity: With the heater disconnected, measure resistance across its terminals. A typical CDA defrost heater will show a finite resistance (often 100–400 Ω). Infinite resistance indicates an open heater.
• 5. Check thermal fuse/defrost thermostat: Many CDA models include a thermal fuse or bimetal thermostat clipped to the evaporator. Test for continuity at room temperature; an open reading suggests failure.
• 6. Replace faulty components: Fit a new CDA defrost heater and/or defrost thermostat/thermal fuse as required. Ensure all connectors are tight and properly insulated.
• 7. If heater circuit tests OK: The main control PCB may not be energizing the heater. This should be diagnosed and repaired by a qualified technician.

After repair: Fully defrost the unit, reassemble, and allow 24 hours of operation to confirm normal frost patterns and that E4 does not return.