After replacing the window regulator of the driver door on my 91 420sel,i lost the central locking on the back doors(will open,but not enough power to close them)also when opening the driver door only,the dome light and courtesylight and the memory seat will not work.However if I open the passenger door or turn the ignition on,those item are working(except for central locking system).I suspect a wire problem in the door.What wire could it be and how do i test it and fix it.I notice the wires go somewhere behind the dash,how far do I need to go?