Power Windows

Power Windows

Electric power windows were introduced into the market in the late 1950s and early 1960s. The basic power window system power is fed through the driver side door through a 20 amp circuit breaker. Power comes into the window switch control panel on the door. There are two contacts on either side of the power contact which would be up and down, that are connected to the vehicle ground in the motor. Power also runs through the lockout switch to a similar switch on either of the doors. This is a new safety feature that prevents kids or pets from opening or closing the windows to keep them safe. When the driver presses a switch one of the two contacts is disconnected from the ground to the center power contact, which keeps the other one grounded. This created a circuit and provides power to the window motor when the switch is pressed the other way, the power goes in the opposite direction. The concept of power windows is pretty simple. There’s a lifting mechanism which uses a linkage to lift the window glass while keeping it level. A small electric motor that is attached to a worm gear and several other spur gears to produce a large gear reduction giving enough torque to lift the window. An important feature of power windows is that they cannot be forced to open. The worm gear that is a part of the drive mechanism enables this. Worm gears have self locking features because of the angle of contact between the worm and the gear. The worm spins the gear but the gear can’t spin the worm. Friction in the teeth causes gears to bind. The linkage has an arm that attaches to a bar that holds end of the window. The end arm slides in a groove in the bar as the window closes. In the other end of the bar is a big plate that has geared teeth cut in it. The motor turns the gear that engages the teeth. The linkage is often used on cars with hand crank windows. Instead of a motor turning the gear, the handle turns it. Power windows are usually inoperable while the car... [continues]

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