How Power Windows Work

Interesting Features

  • Automatic Up/Down - The automatic-down feature is fairly common on cars with power windows. You tap and release the down switch and the window goes all the way down. This feature uses a circuit that monitors the amount of time you hold the switch down. If the switch is 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 for longer than that, the window will stop when you release the button. Automatic-up windows are less common. The problem with automatic-up windows is that if anything gets in the way of the window, such as a child, the window has to stop moving before it hurts the child. One way that carmakers 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 the window goes back down.
  • Window Control From Outside - On the Volkswagen in the TV commercial, 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 more than a set amount of time, the driver's door module lowers the windows.
  • 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 roll your window up. The power-window circuit will have 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, it stays closed until you open a door.

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