A broken window regulator is easy to identify. If you have power windows and suspect your window regulator has failed, you can press your switch button and hear the motor turning but the window glass doesn't move. If you press your window switch and hear nothing, then the problem is likely an electrical one; check your switch or motor. You can tell a manual window regulator is broken when you can completely spin the window crank with no resistance OR if you simply can't turn it at all. Either way, your window glass won't move up or down and the problem lies somewhere inside that door shell of yours. It's your window regulator that you need to replace, and they don't last forever. The gears, springs, pulleys, cables, and all the other parts inside a window regulator have a finite lifespan - a limited number of up and down movements. And when that number has been reached, your window regulator will work no more.
Max Brose debuted the first window regulator for automotive applications in 1928. It was a simple crank drive design with a wrap spring brake in the center to hold tension and keep the window in position. 30 years later, the power window regulator hit the market and became an instant favorite for drivers of luxury vehicles. Currently, modern window regulators have a sensor built into the track which detects the introduction of objects into the path of the glass. If the path is interrupted, the regulator will stop pushing the window up. This is known as "pinch-protection." While designs have migrated away from one large sprocket wheel acting driving the movement of the glass and toward a system of pulleys and cables moving the glass up and down, no window regulator has ever been made with an infinite working life. That means changing a power window regulator or manual window regulator is inevitable for any car owner.
Depending on your vehicle, removing and replacing your window regulator can be and easy to moderately difficult task. You will have to have some basic automotive tools such as ratchets, screwdrivers, pliers, grease, tape, etc. Since the procedure will vary slightly from car to car, use these steps as a guideline and adapt accordingly.