BoilerFaultCodesYour boiler is struggling to breathe because the pipes that take exhaust gases away or bring fresh air in are restricted or blocked.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue and/or air supply duct is blocked.
What causes this fault?
This fault occurs when the boiler's internal safety sensors detect that air cannot flow freely into the unit or exhaust gases cannot exit through the flue pipe. The most common reasons are a physical blockage in the external pipework, such as debris or a bird's nest, or a mechanical failure of the fan which is responsible for pushing these gases out.
This fault is more common during the autumn and winter months, as fallen leaves or heavy snow can physically obstruct the external flue terminal.
DIY fix possible
Check the external flue terminal on your outside wall for obstructions like bird nests, leaves, or debris.Ensure there are no items like garden furniture or storage boxes blocking the flue outlet.Clear any heavy snow or ice buildup from the end of the flue pipe.Reset the boiler once to see if the fault clears after removing external obstructions.
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A boiler cover plan would cover faults like F018 — no call-out fees, no surprises.
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Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
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