BoilerFaultCodesYour boiler has detected an issue with the air flow or ventilation system, preventing it from firing up safely.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: The diagnostics will indicate the nature of the fault to assist a speedy and effective repair
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that the fan isn't moving enough air to safely clear exhaust fumes. The most common reasons are a buildup of debris in the fan or air tubes, or a mechanical failure in the switch that confirms the boiler is venting correctly. Because the boiler cannot guarantee a safe flow of air, it prevents the burner from lighting as a protective measure.
This issue can be more frequent during periods of high winds, which can create back-pressure in the flue and 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.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like Air pressure switch (if fitted) — no call-out fees, no surprises.
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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.
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