BoilerFaultCodesYour boiler has detected that a vital safety switch is stuck in the 'on' position, preventing the system from starting its safety checks.
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 switch made.
What causes this fault?
This fault occurs when the boiler's internal safety sensor thinks the fan is already running before the start sequence has even begun. The most common reason is a mechanical failure within the air pressure switch where the internal contact has become stuck, or moisture has built up in the narrow sensing tubes. Because the boiler cannot verify that the fan is starting correctly from a 'zero' state, it shuts down for safety.
This issue can be more frequent during the first cold snap of autumn when a boiler that has been idle over summer is suddenly forced to work hard, causing aged mechanical switches to seize.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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