Your boiler has stopped working because its internal thermometers are giving conflicting readings and believe they have been fitted to the wrong pipes.

Fault: Temperature sensor The flow and/or return temperature sensors have been installed on the same pipe/incorrect pipe Temperature sensor not connected or is connected incorrectly

What causes this fault?

This fault occurs when the boiler's internal sensors detect that the flow and return pipes are heating up in the wrong order or at unexpected rates. The most common reason is that the temperature sensors have been physically clipped onto the wrong pipes during a repair, or the wiring harness has developed a fault that sends conflicting signals to the main control board.