To repair the power windows of a car, disconnect the battery's negative cable, take out the door panel, and disconnect the wiring of the power window and door lock. Then, determine if the fault lies with fuses, the motor or the switch of the power window, and replace the faulty parts.
Begin repairing the power windows of a car by locating the vehicle's battery beneath the hood. After disconnecting its negative cable, remove the trim pieces, and unscrew the screws or bolts securing the door panel. To remove the panel, pry it out from its retaining brackets.
To determine the fault with the power window, connect voltmeter leads to the power connector's terminals. Turn the car's ignition to on, and press the power window switch. If the voltmeter registers a voltage change, it indicates that the switch is working.
If not, check for any loose connections in the wiring of the switch. If there are no loose connections, note the switch's ground and power wiring, and replace it. Also, inspect if any fuses for the power window are blown out, and replace accordingly.
If the switch works, but the power window does not, it indicates a faulty motor. To replace it, undo the retaining bolts that secure the motor to the window. Tilt and lift out the glass of the door, undo the motor bolts, remove the motor through the opening in the door panel, and replace with a new one.
Secure the new motor with bolts, restore the electrical connectors of the motor and the switch, and replace the glass. Test for proper installation, and reassemble the door panel.