Your boiler has detected a communication issue or a component failure within its central heating temperature sensing system, meaning it cannot accurately monitor the water temperature for your radiators.

Check the CH sensor and panel control and/or the wires connecting them to the PCB (indicates a fault with the CH sensor or its connections).

What causes this fault?

This fault occurs when the boiler's main computer loses contact with the sensor that monitors the temperature of the water heading to your radiators. It is usually caused by the internal sensor failing due to age or a loose wire connection preventing the signal from reaching the control board. Because the boiler cannot tell how hot the water is, it stops heating as a safety precaution to prevent overheating.