The most common reasons for failure are:

• a blown fuse;
• failure of the electric motor which powers the mechanism;
• oxidation of contacts;
• torn wiring.

For all of the cases listed above, the window won’t react to the button being pressed. If it is still possible to control the windows using the buttons on the driver’s door, check the voltage supplied to each door mechanism.

Windows can move jerkily if guide rails or drive gears are worn out or very dirty. Over time, they can also get jammed and stop functioning. In this case, the mechanism should be serviced in accordance with the car manufacturer’s recommendations. Sometimes, condensation or foreign objects in the mechanism can cause the window to stop working. Getting rid of these will make the window function normally again.

This can normally be found in the common fuse box. Depending on the car model, the fuse box can either be under the bonnet or in the car interior under the steering column, near the glove box, or under the rear seat. The marking and exact location of the window regulator fuse will be detailed in the vehicle owner’s manual. In some cases, a fuse in the car comfort control unit or one installed on the driver’s door is responsible for raising or lowering the window.

In order to remove a window regulator mechanism, you should remove the door trim panel, inner door handle, and, in some cases, the armrest and audio system speaker. The specific procedure will depend on the vehicle’s model and where the component is located – in the front or rear of the car. Before removing the window regulator control unit or buttons, disconnect the negative battery terminal. Use a clip removal tool to loosen the door trim panel fasteners, in order to avoid damaging the parts. Remove the panel and take out the control switch along with its trim cover. If you are installing a new handle for a manual window, the door does not need to be disassembled.

For this, place the removal tool in the gap between the handle and the panel and carefully pry the component off. Avoid sudden movements as the fastener can fly off.