Freezer displays E4 and may not defrost; ice accumulates on the evaporator and airflow is restricted.

Safety first: Unplug the freezer. The defrost heater operates at mains voltage and can be hazardous if energized.

Access the heater:

• Remove drawers and the rear interior panel to expose the evaporator and heater assembly.
• The heater is typically a metal or glass-encased element mounted beneath or around the evaporator coil.

Check for obvious damage:

• Look for burn marks, broken heater tubes, or melted connectors.
• Inspect wiring from the heater to the harness for signs of overheating.

Test the heater:

• Disconnect the heater leads from the harness.
• Measure resistance across the heater terminals with a multimeter. A typical reading is between 50–300 Ω depending on model. An open circuit (OL) indicates a failed heater.

Check wiring and board output:

• Verify continuity from the heater connector back to the main control board.
• Inspect the board for burned traces or a damaged defrost relay.

Corrective actions:

• Replace heater: If open or visibly damaged, install a new Blomberg-compatible defrost heater. Secure it in the original clips and ensure it does not touch plastic parts.
• Repair wiring: Replace any burned connectors and damaged wires using high-temperature-rated wire and connectors.
• If the heater and wiring are good, the main control board defrost relay or triac may be faulty and the board should be replaced.

Test: Reassemble, restore power, and monitor over several days to ensure normal frost pattern and that E4 does not reappear.