BoilerFaultCodesTechnical description
fan overrun
What causes this fault?
This status occurs when the internal fan continues to run for an extended period after the boiler has stopped firing to dissipate excess heat from the heat exchanger. It is often caused by heat lingering in the system due to poor water circulation or a pump that isn't moving hot water away fast enough. In some cases, it can also be a sign that the main control board is misreading the temperature sensors.
This is more common during winter months when the boiler is running at higher temperatures for longer periods, leading to more residual heat that needs to be cleared.
DIY fix possible
Check if the heating or hot water has recently reached its target temperatureObserve if the fan switches off naturally after a few minutesEnsure there is no external heat source affecting the boiler