BoilerFaultCodesTechnical description
Mounting fault S3
What causes this fault?
This fault occurs when the boiler's control board loses signal or receives an unexpected reading from the sensor mounted on the main heat exchanger. The most common reason is a loose or damaged connection in the internal wiring, or the sensor itself has developed an electrical fault and can no longer report data correctly. In some cases, it can also indicate that the main circuit board is failing to process the signals it receives from the safety components.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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