BoilerFaultCodesTechnical description
Mounting fault S3
What causes this fault?
This fault occurs when the S3 sensor, which monitors the temperature within the heat exchanger, is not properly seated against the pipework or has physically detached. The most common reason is a loose or damaged retaining clip, but it can also be triggered by a faulty wiring connection that prevents the boiler's computer from receiving an accurate reading.
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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