On this picture you see the fitting on the euro torch side the big threaded hole is for the power wire (voltage /amperage) and gas flows, the 2 back wires are the tigger wires. When you press the trigger you close the eletric circuit that makes the control board turn on the main transformer and the rest, when you realese the trigger you open the circuit and the transformer stops..
You could post the wires and the torch the old and new so we can help you out.