Refrigerator shows F09 or similar defrost error, heavy ice buildup on evaporator, poor cooling

Safety first: Unplug the appliance before accessing the evaporator area or electrical components.

Steps:

• 1. Confirm frost pattern: Remove the rear interior panel of the freezer or refrigerator (depending on model) and inspect the evaporator. A solid block of ice indicates defrost failure.
• 2. Manual defrost: Unplug the unit and allow all ice to melt completely. Use towels to absorb water. Do not use heat guns or open flames.
• 3. Locate defrost heater: The heater is usually a metal or glass-encased element clipped to the bottom or around the evaporator coils.
• 4. Check continuity (advanced): Disconnect heater leads and measure resistance with a multimeter. Infinite resistance indicates a failed heater.
• 5. Inspect defrost thermostat: The thermostat or thermal fuse is clipped to the evaporator tubing. Check for continuity when cold (below its cut-in temperature). An open reading when cold suggests failure.
• 6. Replace faulty parts: Install a genuine V-ZUG defrost heater and/or defrost thermostat as required. Ensure good contact with the evaporator and correct wiring.
• 7. If heater and thermostat are OK: The main control board may not be initiating defrost. This requires further diagnosis and likely PCB replacement.

Warning: The defrost heater operates at mains voltage. Ensure the appliance is unplugged before testing or replacing it.