Your boiler has detected a problem with the fan that clears exhaust gases, preventing it from starting safely for heating or hot water.

Problem with fan, possibly no signal

What causes this fault?

This fault occurs when the boiler's control board sends a command for the fan to spin but does not receive the necessary speed signal back to confirm it is running safely. The most common reasons are a mechanical failure of the fan motor, loose electrical connections between the internal components, or a faulty circuit board that can no longer process data.