BoilerFaultCodesYour boiler is performing a routine start-up check by running the internal fan before the burner ignites.
This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.
Technical description: fan pre-run
What causes this fault?
This is a normal operational stage and not an actual fault with your boiler. It occurs because the boiler's internal computer is running the fan to clear the combustion chamber of any lingering gases before the burner safely ignites. You will likely see this code for a few seconds every time you turn on your heating or hot water tap.
DIY fix possible
This fault may be fixable without an engineer. Check your manual first.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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A boiler cover plan would cover faults like S.11 — no call-out fees, no surprises.
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