BoilerFaultCodesYour boiler has stopped working because one of its internal heat sensors has come loose or is not sitting correctly against the pipework.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Mounting fault sensor S1
What causes this fault?
This fault occurs when the main flow sensor, which monitors the temperature of the water leaving the boiler, loses physical contact with the internal pipework. The most common reason is that the Retaining clip has become loose or broken, preventing the sensor from getting an accurate reading and causing the boiler to shut down for safety. In some cases, it may also be caused by a faulty wiring connection between the sensor and the main control board.
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 F015 — 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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