Your boiler is likely struggling to provide hot water or maintain the correct temperature because its internal hot water thermometer has stopped working.

Fault on Hot Water Sensor

What causes this fault?

This fault occurs when the boiler's internal thermometer for hot water fails to send a clear signal to the main control board. The most common reason is that the sensor has physically degraded or corroded over time, meaning the boiler can no longer tell how hot the water is and shuts down for safety. Occassionally, this can also be caused by loose or damaged wiring connecting the sensor to the rest of the unit.