E3 error on display, freezer may not defrost properly and ice builds up on the rear panel.

Safety first: Unplug the appliance and be prepared for water from melting ice.

Steps:

• Defrost the unit: Open the door and allow the freezer to defrost fully (use towels to catch water). Do not chip ice with sharp tools.
• Access defrost components: Remove the rear interior panel to expose the evaporator and defrost components.
• Locate defrost thermostat/sensor: It is usually clipped to the evaporator tubing or mounted on the evaporator frame.
• Test thermostat: If it is a bi-metal thermostat, check continuity with a multimeter when it is cold (below its closing temperature). It should show continuity when cold. If open when cold, replace.
• Test NTC sensor: If it is an NTC type, measure resistance and compare to expected values. Replace if open/shorted or clearly out of range.
• Check wiring: Inspect the harness from the sensor/thermostat to the main PCB for breaks or burnt connectors.
• Replace faulty parts: Install a new Grundig defrost thermostat or defrost NTC sensor as required, ensuring it is firmly clipped to the evaporator tubing.
• Reassemble and power on: Refit panels, restore power, and verify that E3 clears after a full cycle.