Refrigerator displays E09 and may not defrost properly, leading to ice buildup on the evaporator and poor cooling.

Safety: Disconnect power before accessing the evaporator or heater. The heater can be very hot during operation.

Diagnostic procedure:

• 1. Observe symptoms: Check for heavy frost or ice buildup behind the rear interior panel of the freezer or refrigerator compartment. This is a sign of defrost failure.
• 2. Access evaporator and heater: Remove drawers and shelves, then remove the rear panel to expose the evaporator coil and defrost heater assembly.
• 3. Inspect wiring and components: Look for burnt or broken heater elements, disconnected wires, or a tripped thermal fuse mounted on or near the evaporator.
• 4. Test heater resistance: With power off and heater disconnected, measure resistance across the heater terminals. An open circuit indicates a failed heater that must be replaced.
• 5. Test thermal fuse/thermostat: Check continuity through the defrost thermal fuse or thermostat. If open at room temperature (and not designed to be open), replace it.
• 6. Replace faulty parts: Install a new Gaggenau-compatible defrost heater and/or thermal fuse as needed. Ensure all connections are secure and properly insulated.
• 7. Control board consideration: If heater and safety devices are good but E09 persists and no power is supplied to the heater during defrost, the main control board's defrost circuit may be defective and require replacement.

Note: After repair, manually defrost any remaining ice and allow the unit to run for 24 hours to confirm normal operation.