Technical description
Not a fault code. Service mode selected to max, press service button to return to normal.
What causes this fault?
This occurs because the 'service' button on the control panel was pressed, which puts the boiler into a manual testing mode. This is usually done by an engineer during a service to force the burner to its maximum output, and the flashing light is simply a status indicator showing the mode is active. It is not an internal component failure, but rather a functional setting that hasn't been switched back to normal operations.
DIY fix possible
Locate the 'Service' button (usually marked with a spanner icon).Press and hold the Service button for a few seconds until the light stops pulsing.The boiler should return to its normal operating mode automatically.