Your boiler has detected an internal electrical glitch or a faulty temperature sensor, causing it to shut down for safety.

Sensor or electronics fault | Check NTC's/connections or electronics defect

What causes this fault?

This fault occurs when the boiler's control system receives conflicting or impossible signals from its internal temperature sensors. The most common reason is an electrical short-circuit or a broken connection within the sensors themselves, which prevents the boiler from safely monitoring how hot the water is getting.