BoilerFaultCodesTechnical description
Thermostat out of calibration or faulty
What causes this fault?
This fault occurs when the mechanical sensing bulb inside the thermostat fails to accurately gauge the temperature of the water. Over time, the internal components can wear out or lose calibration, meaning the boiler can no longer safely determine when to turn the burner off. This leads to the system shutting itself down to prevent the water from reaching dangerously high temperatures.
This issue often becomes apparent in autumn when the heating is first switched back on after summer, as the moving parts within the thermostat can seize up through lack of use.
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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