The drivers side windscreen wiper on a fiat punto has stopped working but the passenger side is fine How can you fix it?

This has just happened to my wifes Punto. Had to replace the wiper motor, as the linkage came apart due to wear. You cannot replace the arms, therefore, new motor. You could just try clipping it back in, but it is doubtful. Lift the bonnet. At the back at the top, just under the windscreen, you will see the arms. The one you are talking about will most probably be lying at the bottom, disconnected. Rip off if you ask me.