BoilerFaultCodesTechnical 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 is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.