Your boiler has stopped working because the burner isn't lighting correctly, likely due to a problem with the internal airflow or the ignition system.

Burner blocked

What causes this fault?

This fault occurs when the boiler's control system detects that the burner cannot sustain a stable flame after several attempts. It is usually caused by a lack of proper airflow or an issue with the sensors that verify the flame is safe to stay on. The most common reasons are worn-out ignition components or a build-up of debris within the burner chamber that prevents a clean light-up.