BoilerFaultCodesTechnical description
Main burner fails to light, pilot burning - Additional controls not calling for heat.
What causes this fault?
This issue occurs because the boiler is waiting for a signal from your external equipment that never arrives. Even though the boiler is ready to work, the wall thermostat, timer, or a motorised valve in your airing cupboard has likely failed or reached its target temperature and isn't sending the 'start' command. It means the boiler itself is often healthy, but the system's brain or its switching components have lost communication.
This fault often surfaces during the first cold snap of autumn when controls that have been dormant all summer are suddenly required to operate.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.