Your boiler is receiving incorrect temperature readings from a secondary part of your heating system, which may be preventing your home from heating up efficiently.

What causes this fault?

This fault occurs when the boiler loses a reliable signal from the sensor that monitors the water temperature in your external system piping. It is usually caused by a physical failure of the sensor itself or a loose connection in the wiring that links it back to the main control board. When this happens, the boiler cannot accurately measure how much heat is needed, leading to inefficient operation or a loss of heating.