Your boiler's hot water sensor has stopped working correctly, which means you may have inconsistent or no hot water.

Fault on Hot Water Sensor

What causes this fault?

This fault occurs when the domestic hot water sensor, which monitors the temperature of the water going to your taps, provides an incorrect or missing electrical signal to the main control board. The most common reason is that the internal sensor has degraded over time or developed a short circuit, preventing the boiler from knowing how hot the water actually is. In some cases, it can also be caused by loose or corroded wiring connections between the sensor and the boiler’s brain.