Ferroli furnace fails to ignite, burner does not light, display shows A01 shortly after a call for heat.

Safety first: Turn off electrical power to the furnace and close the gas isolation valve before removing any covers. Wait for all hot surfaces to cool. If you smell gas continuously, do not attempt repair—ventilate the area and contact your gas supplier or a licensed technician immediately.

Step-by-step checks:

• Reset the boiler/furnace: Use the reset button on the Ferroli control panel. If A01 returns repeatedly, continue with checks.
• Check gas supply: Confirm other gas appliances work. Ensure the Ferroli furnace gas isolation cock is fully open. If there is no gas to any appliance, contact your gas provider.
• Inspect ignition electrode and lead: Remove the combustion chamber cover (sealed chamber may require a licensed technician). Look for cracked porcelain, carbon buildup, or a loose ignition lead connection on the ignition transformer and electrode. Clean light deposits with a non-metallic abrasive pad and re-seat the lead firmly.
• Check burner and injector: Visually inspect the Ferroli burner for heavy rust, soot, or debris. If blocked, carefully vacuum and brush the burner surface. Do not enlarge injector orifices.
• Flame sensor (ionisation electrode): Clean the metal tip with fine emery cloth. Ensure the electrode is correctly positioned in the flame path as per Ferroli service manual.
• Gas valve operation (basic check only): With power off, check that the wiring harness to the Ferroli gas valve is firmly connected and not damaged. Do not attempt to adjust gas valve settings without combustion analysis equipment.

When to call a professional: If A01 persists after cleaning electrodes and confirming gas supply, a licensed gas technician should test gas pressure, ignition transformer output, and replace the gas valve or electrodes as needed.