Power Window Operation
WARNING: This page is about a different car, the 2002 GMC Safari and 2002 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
The normally closed contacts of the power window switch are connected to ground and the center pole is connected to the accessory voltage circuit. By placing the either power window switch in the down position, voltage is applied to the power window motor down circuit and to the power window motor. The other side of the power window motor is connected to ground through the normally closed contacts of the power window switch through the power window motor up circuit and drives the window down.
By placing the power window switch in the up position the polarity of the motor is reversed and the motor drives the window up.