BoilerFaultCodesYour boiler has stopped working because it cannot confirm that the fan is safely clearing waste gases from the system.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Air Proving LOCKOUT
What causes this fault?
This fault occurs when the boiler's internal safety sensor cannot detect that the fan is successfully pushing exhaust gases out of the flue. It is often caused by a failing fan motor, a perished vacuum tube, or a faulty air pressure switch that is no longer accurately measuring the airflow. If the boiler cannot confirm it is venting safely, it will shut down to prevent the build-up of harmful gases.
This fault can sometimes be triggered during periods of high winds, which can create back-pressure in the flue that prevents the air pressure switch from closing correctly.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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