BoilerFaultCodesYour boiler has stopped working because it cannot detect a stable signal from the sensor that monitors exhaust gases, often due to a loose wire or a faulty internal component.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flue sensor open circuit
What causes this fault?
This fault occurs when the boiler's control board loses communication with the sensor that monitors the temperature of the exhaust gases. It is usually caused by a wire vibrating loose over time, moisture affecting the electrical connections, or the sensor itself failing due to constant exposure to high heat. When this signal is lost, the boiler shuts down as a safety precaution to ensure it isn't venting gases at dangerous temperatures.
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 F08 — 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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