BoilerFaultCodesYour boiler has detected a problem with how air and waste gases are moving through the system, causing it to shut down for 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 Pressure Fault (fan, air pressure switch, flue, or venturi).
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that the fan isn't moving enough air or that the exhaust gases aren't leaving the building correctly. The most common reason is a buildup of dirt in the small tubes known as the venturi, or a mechanical failure in the fan or air pressure switch. Because the boiler cannot guarantee that harmful fumes are being safely removed, it shuts down immediately as a safety precaution.
This fault is more common during periods of high winds, which can cause pressure fluctuations in the flue that interfere with the air pressure switch readings.
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 FAIL POINT J — no call-out fees, no surprises.
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