BoilerFaultCodesYour boiler has detected that its internal temperature sensors are giving conflicting readings or have been incorrectly wired.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: S1 and/or S2 sensor exchange
What causes this fault?
This fault occurs when the boiler's control board detects that the two internal temperature sensors are reading values that do not match each other or have been swapped. It often happens if a sensor has developed a chemical fault or if the electrical wiring connecting them to the main computer has become loose or damaged. Because the boiler cannot accurately verify the water temperature, it shuts down as a safety precaution.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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