Boiler locks out with A01 on display, burner does not ignite, fan may start briefly then stop

Safety first: Turn off electrical power to the IVT boiler at the isolator and close the gas isolation valve before removing any covers. Only a Gas Safe / certified technician should work on gas components.

Basic checks a homeowner can do:

• Reset the boiler: Follow the IVT user manual to perform a reset. If A01 returns immediately, do not keep resetting.
• Check gas supply: Ensure other gas appliances (if present) work. If not, contact your gas supplier.
• Check flue terminal: Go outside and make sure the flue outlet is not blocked by leaves, snow, or debris.

Technical checks (for qualified technician):

• Remove the combustion chamber cover and inspect the burner for heavy soot or debris. Clean or replace the burner insert as per IVT service instructions.
• Inspect the ignition electrode and ionisation electrode: check for cracks in the ceramic, correct gap, and secure connections to the ignition transformer/PCB. Replace electrodes if worn or damaged.
• Verify the gas valve coil resistance and that the valve receives the correct voltage from the control board during ignition. If voltage is present but valve does not open, replace the gas valve assembly.
• Check the flame signal in diagnostic mode (if available on the IVT model). If flame is present but not detected, replace the ionisation electrode or PCB as per IVT procedures.

Do not attempt to adjust gas valve settings without proper combustion analysis equipment and manufacturer data.