If your car has a power rear window, it has a motor and a regulator, sometimes called a “transmission”. This configuration is used in all power windows, although your power rear glass setup is a little bit different from what you’ll find behind the door panel on the driver or passenger doors. However, the way they work is pretty similar.
When you press the button to open the rear glass, the motor produces rotational motion. This must be translated into either vertical or horizontal movement depending on the style of window in question. That’s what the transmission does. It’s usually made of metal and looks something like a big pair of scissors. As the motor turns, the transmission opens and closes. This moves the window in the desired direction.
The same factors that affect your other windows will affect the rear window transmission. Primarily, the issue is one of use rather than time or mileage. If you use the back glass heavily, it puts wear and tear on the rear window transmission (which must move every time you open or close the window). Over time, this will damage the transmission and it will need to be replaced.
If the regulator/transmission fails completely, the back glass will not open or close. It may be stuck open, which will allow exhaust fumes, heat or cold from outside, rain and other elements into your vehicle.
The symptoms of a failing rear window transmission are relatively easy to spot. They include:
- The window moves with a jerking motion
- The window does not move at all
- There is an unusual noise when the window moves, such as a scraping, grinding of squealing
- The window only opens or closes partially
- The window closes crooked
If your rear window is experiencing any of these symptoms, chances are good that the rear window transmission is about to fail. A certified mechanics can inspect the system and replace the rear window transmission if necessary.