BoilerFaultCodesYour boiler has switched itself off because it has detected that dangerous exhaust fumes are not escaping through the chimney correctly.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: The Burner On neon will extinguish, but Flame Failure and Boiler Safety Overheat neons will not illuminate. Occurs if the flue becomes blocked or is subjected to adverse conditions.
What causes this fault?
This fault triggered because the internal safety device detected that harmful waste gases were flowing back into the room instead of leaving through the chimney. This is usually caused by a physical blockage in the flue, such as bird nests or debris, or severe external air pressure preventing the fumes from escaping. The boiler shuts down immediately to prevent carbon monoxide from entering your living space.
This fault is more common during periods of high winds, which can push air back down the chimney, or in autumn when falling leaves and nesting birds are more likely to obstruct the flue.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
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A boiler cover plan would cover faults like Flue Safety Thermostat Activation — no call-out fees, no surprises.
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