Car doors are wired in many different ways, depending on which features are incorporated. We'll go through the wiring on a basic system -- one that allows the driver to control all four windows on the car and can lockout the controls on the other three individual windows.
A Basic System
On this system, the power is fed to the driver's door through a 20-amp circuit breaker. The power comes into the window-switch control panel on the door and is distributed to a contact in the center of each of the four window switches. Two contacts, one on either side of the power contact, are connected to the vehicle ground and to the motor. The power also runs through the lockout switch to a similar window switch on each of the other doors.
A simple power-window circuit
When the driver presses one of the switches, one of the two side contacts is disconnected from the ground and connected to the center power contact, while the other one remains grounded. This provides power to the window motor. If the switch is pressed the other way, then power runs through the motor in the opposite direction.
An Advanced System
On some cars, the power windows work in a completely different way. Instead of the power for the motor going through the switches directly, the switches are connected to one of the many electronic modules in the car (the average car contains 25). Some cars have one in the driver's door, as well as a central module called the body controller.
Cars that have lots of controls on the door are more likely to have a setup like this. Some cars have the power-window, power-mirror, power-lock and even power-seat controls all on the door. This would be too many wires to try to run out of the door.
Instead of trying to do that, the driver's door module monitors all of the switches. For instance, if the driver presses his window switch, the door module closes a relay that provides power to the window motor. If the driver presses the switch to adjust the passenger-side mirror, the driver's door module sends a packet of data onto the communication bus of the car. This packet tells the body controller to energize one of the power-mirror motors.
Power Window FAQ
How do power windows work?
Power windows work via an electronic motor that's attached to a worm gear, which is attached to several other gears. Altogether, these parts create torque and that torque lifts the window.
Can you convert manual windows to power windows?
Manual windows can be turned into power windows, but it does require quite a bit of work. From wiring to additional in-door mechanisms, there are many components that have to be added to take windows from crank-powered to motor-powered.
How much does it cost to add power windows to a car?
To add a window regulator and motor — as well as all the other parts needed for power windows — you can expect to pay as much as $850 in parts alone.
When did cars get power windows?
Power windows were first introduced on luxury models in the 1940s.
Do power windows work when the car is off?
You do need power in order to operate power windows. Your car either needs to be running or you need to turn the car's power on (usually called "accessories" mode).