Your boiler's temperature sensor has stopped working correctly, meaning the system can no longer tell how hot the water is and has shut down as a precaution.

If a fault occurs with the boiler thermostat the fault display screen will show "C/H Sensor Fault".

What causes this fault?

This fault occurs when the internal sensor responsible for monitoring water temperature becomes damaged or loses its ability to send an accurate electrical signal. The most common reasons are electrical failure within the thermistor itself or corrosion on the wiring connections caused by years of heat cycling.