Power windows are found in most late-model automobiles; and when everything is powered, there is the potential for a motor to go bad. When assessing a power window motor, it is important to check alternative sources for the problem before blaming the window motor. Troubleshooting the problem yourself can also save you some time, even if you need to bring the vehicle in to a mechanic. If none of the window buttons opens the windows, this does not automatically indicate a bad motor.
Locate the fuse compartment that houses the fuses for the window motors. In vehicles manufactured after 1985, the fuse for the window motors is Fuse 4 (30A), and it will be in the central electrical panel. Refer to the owner's manual for your vehicle if you have difficulty locating the central electrical panel. Assess the fuse. If it has blown, replace it with a fuse of the same amperage. Test the window for operation. On vehicles built before 1985, the fuse is Fuse 8 (16A), and it will be in the additional fuse panel. Your owner's manual will list the locations of all the fuse boxes in your vehicle. There are usually fuse boxes under the bonnet (labelled "Fuses") and one in the dashboard (typically on the driver's side). Newer cars have multiple fuse box locations, including the side of the centre console or on the passenger's side of the dash.
Test the power window relay. The power window relay is located on the Central Electric Panel in vehicles built after 1985 and typically on the lower left-hand side of the centre console on pre-1985 models. Remove the power window relay and jumper terminal 30 and terminal 87. Test the power windows after the jumper is installed. This will tell you if the motor is still working or needs replacement. This will also rule out if there is something other than the motor at fault for the problem. If the windows work with the jumper installed, the motor is still functioning properly.
Check the window switch next. The window switch must be exposed from inside of the door panel in order to test it. Use a voltmeter or ohmmeter to check the window switch. Terminals 4 and 5 should read 12VDC or close to it. Terminals one-four (a connection of terminal one to terminal four) and two-three (terminal two to terminal three) should read less than 1 ohm with the ohmmeter when the window switch is open, and low resistance from terminals one-three and two-five when the window switch is closed. Low voltage indicates a problem with the window switch and possibly the motor.
To reduce the risk of damaging the window switch, motor, door panel or other vital parts, it may be best to leave the door panel intact and allow a mechanic to inspect the problem beyond the fuses.