BoilerFaultCodesYour boiler is in a normal startup phase where it clears any leftover gas from the combustion chamber before lighting, but it has become stuck at this stage.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Pre-purge
What causes this fault?
This fault occurs when the boiler's fan fails to reach the required speed or the system cannot confirm that air is moving safely through the unit. Because the boiler cannot verify that the combustion chamber is clear of old gases, it stays in this holding pattern as a safety precaution rather than moving to the ignition stage. The most common reasons are a failing fan motor, a blocked air flue, or a faulty sensor that isn't reporting the airflow correctly.
This issue can sometimes be triggered during very windy weather, as strong gusts can create back-pressure in the flue that interferes with the fan's ability to clear the chamber.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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