Your boiler has detected a problem with the internal ignition components, meaning it cannot safely light the burner to provide heat or hot water.

Fault: Ignition transformer cable Ignition transformer cable harness not connected to the main PCB or it is connected incorrectly, short circuit in the cable harness or damaged ignition transformer

What causes this fault?

This fault occurs when the boiler's control board loses communication with the components responsible for creating the spark and sensing the flame. It is usually caused by a loose connection, damaged wiring, or electrodes that have worn down and can no longer complete the electrical circuit required to start the boiler. Without this secure connection, the system shuts down as a safety precaution to prevent unburnt gas from entering the combustion chamber.