BoilerFaultCodesYour boiler has detected a safety issue with how it clears exhaust fumes, causing it to shut down to prevent potential danger.
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 DEVICE: The appliance will enter a lockout condition in the event of an air flow fault. If the controls fail to detect the correct air flow through the appliance the electricity supply to the gas valve will be interrupted.
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that harmful exhaust fumes are not being properly cleared from the unit. The most common reasons are a failing fan that cannot push the air out, or a blockage in the flue pipe that leads outside. Because the boiler cannot guarantee it is operating safely, it automatically cuts the power to the gas supply to prevent a hazard.
This issue can sometimes be triggered by high winds blowing directly into the external flue pipe, which creates back-pressure that the fan cannot overcome.
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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A boiler cover plan would cover faults like Domestic water demand indicator flashes (approximately five times per second) — no call-out fees, no surprises.
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