BoilerFaultCodesYour boiler has detected an internal communication error or a connection issue with a thermal sensor, causing it to shut down for safety.
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 S3
What causes this fault?
This fault occurs when the boiler's control board loses signal or receives an incorrect reading from a specific internal temperature sensor. The most common reason is that the sensor itself has failed due to wear, or the wiring connecting it to the main computer has become loose or damaged.
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 f016 — 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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