BoilerFaultCodesYour boiler has stopped working because one of its internal heat sensors is reporting a fault, meaning the system can no longer safely monitor the water temperature.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Sensor fault S1
What causes this fault?
This fault occurs when the boiler's main flow sensor sends an incorrect or interrupted signal to the control board, preventing the system from knowing if it is safe to fire. The most common cause is a physical failure of the sensor’s internal components, though it can also be triggered by loose or corroded wiring connections that break the electrical circuit.
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 F031 — 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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