If your rear windows are *not* going even as far down as they should, then you're likely dealing with a mechanical or electrical problem:
* Check the window regulators: These are the mechanisms that control the up-and-down movement of the glass. They can wear out, break, or become jammed with debris.
* Inspect the window motors: These are the electric motors that power the regulators. A faulty motor prevents the windows from moving.
* Examine the wiring: Check for broken, frayed, or disconnected wires in the door harness. These wires supply power to the motors.
* Look for obstructions: Something might be blocking the window from going down, like a child's toy or a piece of trim.
If you've determined it's not a design limitation and the windows aren't functioning correctly, you'll likely need to take the car to a mechanic or an auto parts store for diagnosis and repair. Trying to fix the window regulator or motor yourself can be challenging, especially without experience.