2000 rear door control box window motor wiring

2000 Deville. Problems with electric window on pass rear door. Wiring on control box has 4 heavy gauge wires on harness clip. 2 of the wires seem to be input. The orange is input hot. The black would seem to be input common. The two others lead to motor for window. It would seem control box reverses polarity for motor to reverse for up and down. The problem seems to be with the black wire that would seem to be the common input. There is no voltage draw when testing it to the orange hot wire. When motor is grounded to the car chassis, and the hot applied, motor operates. When switch polaritiy to motor it reverses. Thus, my question is what should the black wire be connected to? Does anyone know if this is fused separately? Is it merely a ground? Had car in rainstorm and window went down by itself. That is what started all of this. Thanks for the help. Joe

The right rear door window regulator broke on my 2000 Deville and I am waiting for the part to come in. I don't know what the black wire should be connected to but I an conduct some tests on the wiring if you have specific tests in mind.

Thanks for the reply. When you are testing, I am just trying to figure out what that black wire is connected to. I am wondering if it is just a ground wire or if it is connected to some other control unit. Thanks. Joe