BoilerFaultCodesYour boiler has detected that dangerous exhaust fumes are being blown back into the appliance instead of exiting through the flue safely.
Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now — this fault can be dangerous if ignored.
Technical description: Down draught thermostat
What causes this fault?
This fault occurs when the safety sensors detect that combustion gases are being pushed back down the chimney instead of escaping outside. The most common reason is an external blockage in the flue or high winds blowing directly into the terminal, preventing the boiler from venting safely.
This fault is more common during periods of extreme high winds or stormy weather, which can create a back-pressure in the flue system.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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A boiler cover plan would cover faults like 16-17 — no call-out fees, no surprises.
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