Boiler locks out with E03, burner starts then shuts down after a few seconds, sometimes with rumbling noise.

Safety first: Switch off power and close the gas shut-off valve. Allow the boiler to cool. Flame instability can cause dangerous combustion.

• Check gas supply stability: If possible, have the gas inlet pressure checked with a manometer during operation. Large pressure drops indicate a supply issue that must be resolved by the gas supplier or a technician.
• Inspect burner head: Remove the burner from the boiler following the Weishaupt service instructions. Check the burner head, mixing plate, and gas ports for soot, rust, or debris. Clean with a soft brush and vacuum; do not enlarge gas ports.
• Clean ionisation electrode: Clean the ionisation electrode and ensure it is correctly positioned in the flame. Replace if the ceramic is cracked or the rod is heavily worn.
• Check combustion air settings: Verify that the air damper or air setting on the Weishaupt burner has not been altered. Incorrect air can cause flame lift-off. Adjustments should only be made with a flue gas analyser by a qualified technician.

When to call a professional: If flame loss persists after cleaning, or if gas pressure or combustion settings need adjustment, contact an authorised Weishaupt service partner.