Your boiler has stopped providing hot water because the internal sensor that measures water temperature has detected a technical fault or a short circuit.

Burner blocked. Short circuit - DHW temperature sensor (combi boiler).

What causes this fault?

This fault occur when the boiler's control board receives an impossible electrical signal from the Domestic Hot Water sensor, suggesting the component has failed internally. It is usually caused by a 'short circuit' where the sensor's internal wiring has degraded or succumbed to moisture, preventing the boiler from safely monitoring how hot your water is. In some cases, the issue may also lie with a loose or damaged cable harness connecting the sensor to the main computer.