Your boiler has detected an electrical fault with the internal fan, which is preventing the unit from starting up for safety reasons.

Fan Connections Short Circuit

What causes this fault?

This fault occurs when the boiler's control board detects an electrical short circuit within the fan system. It is usually caused by water ingress onto the electrical components, a degraded internal wiring harness, or a failure in the fan motor's windings. For safety, the boiler will prevent the ignition sequence until the electrical circuit is restored to a safe state.