Your boiler has detected a problem with the sensor that measures hot water temperature, which means your taps may not get warm.

Domestic hot water temperature sensor (NTC) fault

What causes this fault?

This fault occurs when the small sensor responsible for monitoring your tap water temperature fails or sends an incorrect electronic signal to the control board. The most common reason is that the internal components of the sensor have degraded over time or developed a small mineral build-up, preventing it from accurately reading how hot the water is.