Your boiler's internal thermometer for the central heating system has stopped working correctly, which means the system cannot monitor or control the water temperature.

Failed heating sensor – issue with heating sensor and could need replacing

What causes this fault?

This fault occurs when the boiler's central heating sensor either develops an electrical short or stops communicating with the main control board. The most common reason is that the internal thermistor has reached the end of its lifespan or has been damaged by constant temperature fluctuations, preventing the boiler from safely monitoring heat levels.