BoilerFaultCodesYour boiler has detected a blockage or a fault in the system that expels exhaust gases, causing it to shut down for safety.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Debris in flue system, Debris in flue venturi, or the boiler or flue system has developed a fault.
What causes this fault?
This fault occurs when the boiler's safety sensors detect that harmful exhaust gases are not being cleared from the system effectively. The most common reasons are a buildup of dirt or debris in the small tubes inside the boiler, a failing fan that cannot spin fast enough, or a blockage within the external flue pipe.
This fault is more common during the autumn and winter months, as heavy winds or nesting debris can obstruct the flue terminal, and cold temperatures can affect the moving parts of the fan.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 03 — no call-out fees, no surprises.
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