BoilerFaultCodesYour boiler has stopped working because it cannot confirm that the internal fan is safely clearing waste 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 safety sensors cannot detect a steady flow of air through the unit. While the fan might be spinning, a blockage in the plastic tubes, a build-up of dirt, or a failing motor prevents the system from proving it is safe to ignite. Because the boiler cannot guarantee that harmful exhaust fumes are being pushed outside, it shuts down as a safety precaution.
This issue often surfaces during the first cold spell of autumn when a fan that has been idle over summer struggles to spin up to the required speed.
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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like Neon 3 NOT lit — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Glow-worm Fuelsaver Complheat 40 55 is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.