Boiler shows A02 and shuts down shortly after ignition, flame lights but then goes out

Safety: Switch off power and close the gas isolation valve if you smell gas or suspect a leak. Ventilate the area and do not use naked flames.

User checks:

• Confirm that the gas meter and main gas valve are fully open.
• Check that other gas appliances are operating normally. If they also fail, contact your gas supplier.
• Perform a single reset from the boiler control panel. If A02 reappears, stop resetting.

Technician checks:

• Measure inlet and burner gas pressures while the boiler is firing and compare with IVT specifications. Correct any supply or regulator issues.
• Inspect and clean the burner and injector for contamination or partial blockage.
• Check the ionisation electrode position and wiring. Replace if the flame signal is weak or intermittent.
• Verify correct operation of the gas valve modulation coil and control signal from the main PCB. Replace the gas valve or PCB if modulation is unstable.

Because this fault involves combustion stability, only a qualified heating engineer should carry out internal work.