Your boiler has detected an issue with the fan that pushes exhaust gases out of your home, causing the system to shut down for safety.

Fan Fault

What causes this fault?

This fault occurs when the boiler's internal computer can no longer control or receive speed signals from the fan that removes combustion gases. The most common reason is that the fan motor has physically burnt out or suffered a mechanical failure, though it can also be caused by loose electrical connections or a fault on the main control board. For safety, the boiler will stop firing immediately if it cannot confirm the fan is spinning at the correct speed.