Freezer shows E4 and may stop defrosting; thick ice forms on the evaporator and airflow is restricted.

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

• Access evaporator and heater: Remove baskets and inner rear panel to expose the evaporator. The defrost heater is usually a metal or glass-encased element clipped to the bottom or woven through the coil.
• Check for obvious damage: Look for burnt spots, broken heater sheath, or disconnected wires.
• Test heater resistance: Disconnect heater leads and measure with a multimeter. Typical values are between 50–300 Ω depending on model. An open circuit indicates a failed heater.
• Inspect defrost thermostat / thermal fuse: Located on or near the evaporator tubing. Test for continuity at freezer temperature; an open thermostat can block heater operation.
• Check wiring and connectors: Follow the heater circuit back to the PCB, looking for burnt connectors or loose spades. Repair or replace damaged wiring.
• Replace faulty components: If the heater is open, install a compatible Teka defrost heater. If the thermostat or thermal fuse is open, replace with the correct temperature-rated part and secure it to the evaporator as originally installed.
• PCB/relay check: If heater and thermostat are good, the defrost relay or triac on the main PCB may be defective. Inspect the board for heat damage and replace the PCB if necessary.

Test: After reassembly, restore power and force a defrost cycle if the model allows (consult service mode). Monitor for proper defrosting and absence of E4 over several days.