Car windows sometimes become misaligned, and in most instances, this is due to either resistance to the up and down movement of the glass or a shock to the car door. As a result, the window will usually fall into the door and become impossible to roll up again. The problem can be annoying, especially if it is raining when it occurs. Fixing it is not difficult, but may require different approaches depending on whether your car has manual or electric windows.
Determine whether the window is misaligned or if there is some other issue causing it to operate improperly. Lower the window all the way down. If the glass does not retract into the door completely the window is off the track. If you raise the window all the way up and the glass does not reach the top of the frame your window is off its track.
Attempt a quick repair first to avoid opening the door panel. Hold the window glass in your hand tightly, and lower the window slowly until the track reaches the bottom of the window. In some cases the window will slot itself back into the track and you will feel a clunk as it does so. This may return the window to operational status but if it does not, go to the next step.
Follow the vehicle or shop manual instructions to remove the inside door panel for your particular make and model car. Typically there will be screws or bolts located around the door handle as well as around the edges of the panel. Snaps also hold the panel in place and can be loosened by sliding a flathead screwdriver between the panel and door frame and wedging the two apart gently, moving all around the edges. Lift the panel away from the door making sure to disconnect any wire clips which may be in the way. Carefully remove the water seal so that you may replace it without damage when the work is done.
Locate the window glass. Power windows have two rubber side rollers which bring the window up and down. If the rollers are worn out, replace them. Set the window glass between the rollers in its normal slot. Raise the window all the way and bring it back down. This should reset its position and get it on track. If you have crank-up windows, there is usually a notch or hole in the glass where the crank arm sits. This can sometimes bend or break and must be shaped back into its original form to make the window operational again.
Reattach the door panel, trim, door handle and any other parts you may have removed.
Leaning on the window glass when it is partially raised places stress on the rollers and crank arms, which could affect their operation. Lower the window all the way and lean on the door frame itself.