BoilerFaultCodesYour boiler has stopped working because it cannot safely confirm that the fan is clearing exhaust gases from the system.
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 internal computer tries to start the fan but cannot confirm that a safe flow of air is moving through the system. The most common cause is either a mechanical failure of the fan itself or a blockage in the small plastic tubes that connect to the air pressure sensor, preventing the boiler from knowing it is safe to ignite.
This issue can be more common during periods of high winds, as strong gusts can sometimes interfere with the pressure sensor's ability to get a stable reading through the external flue.
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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