E4 error displayed, freezer may not defrost and thick ice forms on the evaporator or rear wall.

Safety first: Unplug the freezer. The defrost heater operates at mains voltage; do not test it live unless you are qualified.

Inspection and testing:

• Access the evaporator: Remove drawers and the rear interior panel to expose the evaporator and heater.
• Locate the defrost heater: It is typically a metal or glass-encased element running along or beneath the evaporator coil.
• Check wiring and connectors: Look for burnt, discoloured, or loose connectors. Repair or replace damaged wiring.
• Measure heater resistance: Disconnect the heater from its connector and measure resistance with a multimeter. A typical heater will read between 50–300 Ω depending on model. If it reads open circuit, the heater is faulty.
• Check thermal fuse (if fitted): Some Grundig models include a thermal fuse in series with the heater. Test for continuity; if open, replace with the correct rated part.
• Replace faulty components: Install a new Grundig defrost heater (and thermal fuse if required). Ensure it is correctly positioned and not touching plastic parts.
• Control board check: If heater and wiring are good but E4 persists, the defrost relay or triac on the main PCB may be defective, requiring PCB replacement.