BoilerFaultCodesYour boiler is struggling to breathe because something is blocking the passage of air or exhaust gases through the flue pipe.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue obstruction
What causes this fault?
This fault occurs when the boiler detects that air isn't moving through the system correctly, usually because something is physically blocking the flue pipe or the internal air pathways. It is often caused by debris like leaves or a bird's nest in the external pipe, or a failing internal fan that can no longer push the exhaust gases out of your home safely.
This fault can be more common in autumn and winter, as high winds can blow debris into the flue or nesting animals may seek warmth inside the pipework.
DIY fix possible
Check the external flue pipe terminal outside your home for obvious obstructions like bird nests, leaves, or debris.During winter, check if the flue outlet is blocked by heavy snow or icicles.Reset the boiler by turning the selector switch to 'R' for five seconds after removing any external blockage.
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A boiler cover plan would cover faults like E53 — no call-out fees, no surprises.
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