BoilerFaultCodesYour boiler has detected a problem with the sensor that monitors the temperature of the water leaving the unit, causing it to shut down to prevent overheating.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Flow temperature sensor error (S1)
What causes this fault?
This fault occurs when the internal control board loses communication with the flow temperature sensor or receives an implausible reading. The sensor has likely failed due to age and heat degradation, or the electrical connection has become loose or damaged, preventing the boiler from safely monitoring heat levels.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
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