Your boiler has detected an issue with the fan that clears exhaust fumes, preventing the system from starting for your safety.

Fan or Fan Wiring Fault

What causes this fault?

This fault occurs when the boiler's control board fails to receive a signal that the fan is spinning at the correct speed to safely expel exhaust gases. The most common reason is that the fan motor has seized or its internal electronics have burnt out, though loose or damaged wiring can also interrupt this vital communication. Without a functioning fan, the boiler automatically shuts down to prevent dangerous fumes from building up inside the unit.