Furnace attempts to start but shuts down with E1, no flame established

Safety first: Isolate electrical power and close the gas isolation valve before working on the burner or ignition system.

• Remove the burner access cover to expose the burner and ignition/ionisation electrodes.
• Inspect the ionisation electrode for cracks, heavy oxidation, or soot. Clean gently with fine emery cloth and a soft brush. Ensure the ceramic insulator is intact.
• Check the electrode gap and position relative to the burner as per the ATAG service manual (typically a few millimetres above the burner surface and in the flame path).
• Clean the burner ports with a soft brush and vacuum to remove dust and debris that can prevent flame formation.
• Verify all earth/ground connections to the burner and control board are tight; poor grounding can prevent flame detection.
• Restore gas and power, then reset the boiler and observe ignition. If sparking is weak or absent, the ignition transformer/spark generator may need replacement.
• If the unit still shows E1 and gas supply is confirmed, contact a certified gas technician to check gas pressure and combustion settings.