how can i repair a window in citroen xantia?

I recently had a problem with my xantia, the drivers window would not go up or down, aftertaking off the inside skin of the door i found the control unit for the window. I found the black lead which should have been grounded was not. I connected between the black lead and one of the ground connections to the passengers side window switch and all is now well

Hywel
April 2006