Have you ever wondered what makes your car windows go up and down? How about the Electric windows with the automatic up feature that raise the window by themselves, but stop going up if there is an obstruction? Or maybe you've seen the Volkswagen AD where the bloke opens the windows by turning the key in the door lock.
The lifting mechanism, this device is the heart of a both manual and Electric window
systems.
The window lift on most cars uses a neat linkage to lift the window glass while keeping it level. A small electric motor is attached to a worm gear and several other spur gears to create a large gear reduction, giving it enough torque to lift the window.
In a basic Electric window system, the power is fed to the drivers door through a fuse.
The power comes into the window switch control panel on the door and is distributed to
contacts in the center of each of the four window switches. Two contacts, one on either
side of the power contact, connect to the motor. I fitted the power also runs through the
child lockout switch to a similar window switch on each of the other doors. When the
lockout switch is thrown, it cuts power to the other door switches.
When the driver presses one of the switches, one of the two side contacts is connected to
the center power contact. 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.
Automatic Up/Down - The automatic down feature is fairly common on cars with power windows. Often you tap and release the down switch and the window goes all the way down. This feature uses a circuit that monitors the time you held the switch down. If the switch was down for less than about half a second the window will go all the way down until it hits the limit switch. If you hold the switch down longer than that, then the window will stop when you release the button.
Automatic-up windows were less common but are common place now. The problem with automatic-up windows was that if anything gets in the way of the window, such as a childs head, the window has to stop moving before it hurts the child. One way that car makers control the force on the window is by designing a circuit that monitors the motor speed. If the speed slows, the circuit reverses the power to the motor so that the window goes back down. Off course if the window gets sticky as they do, the motor will resolutely refuse to lift it
Window Control From Outside - On the Volkswagens in the AD the windows can be lowered by inserting the key in the driver's door, turning and holding it. This feature is controlled by the driver's door module, which monitors a switch in the door lock. If the key is held turned for over a set amount of time, the driver's door module lowers the windows. ( why you would want to do this iM NOT REALLY sure suggestions welcome)
Courtesy Power-On - Some cars maintain the power to the window circuit after you turn your car off, which saves you from having to stick your key back in the ignition if you forget to put your windows up. The electric window circuit has a relay on the wire that provides the power. On some cars, the body controller keeps this relay closed for an extra minute or so. On other cars, the relay stays closed until you open a door.