BoilerFaultCodesYour boiler has detected that the internal fan is not moving air correctly, so it has stopped the ignition process for your safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Air flow proving fault - that is fan or air pressure switch
What causes this fault?
This fault occurs when the boiler's safety system cannot confirm that the fan is spinning fast enough to clear waste gases. The most common reasons are a build-up of dirt within the fan assembly or a blockage in the small plastic tubes that sense air movement. Consequently, the boiler stays in a 'pre-ignition' state and won't light the burner because it cannot guarantee the flue is clear.
This fault can be more frequent in autumn or during high winds, as debris like leaves can enter the flue terminal and obstruct the airflow.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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