Your boiler has stopped working because the internal fan, which safely clears exhaust gases, isn't spinning at the correct speed.

Fan speed incorrect See chart

What causes this fault?

This fault occurs when the boiler's processor detects that the fan is not rotating fast enough to safely expel waste gases from the flue. The most common reasons are a build-up of dirt within the fan housing, worn-out bearings that cause the motor to seize, or a communication failure between the fan and the main control board.