Display shows E3; unit fails to ignite or shuts down during ignition sequence.

Safety: Turn off power. Close the gas shutoff valve. Only qualified personnel should adjust gas components.

• Verify gas supply: Ensure the external gas shutoff valve is open and that other gas appliances in the building operate correctly. If not, contact the gas supplier.
• Check ignition electrode: Access the burner and inspect the ignition electrode for cracks, carbon buildup, or misalignment. Clean and adjust gap per Buderus specs.
• Inspect burner: Remove and clean the burner head if accessible. Look for debris, rust, or spider webs blocking ports. Clean with a soft brush and compressed air.
• Check ignition cable: Inspect the high-voltage cable for damage and secure connections at both the electrode and control board.
• Gas valve and pressure: If ignition still fails, a technician should measure inlet and manifold gas pressure and test the gas valve operation with proper instruments.
• Reassemble and test: After cleaning and inspection, reassemble all components, restore gas and power, and attempt ignition while monitoring for safe operation.