How to Diagnose Power Window Failures

A power window is one of the components that fail quite often, depending on how much you use it. Another reason for failure is if the operator holds the switch after the window is completely up or down, keeping the power window motor running while the window is at a complete stop.

Check for power to the main switch. Operate the windows at the main control on the driver's door first, noting which power window has failed. Operate the window from the switches on each door. Make sure that you do not have the window lock button on. If at least one of the windows work while using the main control on the driver's door, you have power to the main control switch.

Listen to the window that has failed to see if you hear the motor turning as you operate the switch. If no sound is emitted from the motor than remove the switch from the door and check it for power. Use a circuit tester and attach the alligator clip to a good ground and probe the back of the switch for power. If power is present than continue, if not then there is a problem stemming from the main switch at the driver's door. If power was present, operate the switch in one direction, then the other, and you should have one terminal at a time show power.

If the switch on the door did not operate the window, then go back to the driver's door main panel and remove it from the door panel and turn it over. See if there is power at the terminals for the respective window. Look for the switch marked for the particular window in question and probe it the same way as with the previous switch. If you do not have power in both directions then the problem is the main switch. The main should have power at all terminals when operated, then it will send power to the secondary switch on the door in question.

If the main switch failed the test then just replace it and that should take care of the problem. If both the switches passed, then there is a problem with the motor or regulator.

Remove the door panel and look at the window regulator for obvious problems such as broken or loose cables, or a loose connector to the motor. The motor has only two wires - one hot and one ground when the switch is energized. If you disconnect the connection at the motor you can test it buy energizing one of the terminals and grounding the other. As you change the polarity and or put power to the opposite terminal you can change directions of the motor. If neither side will operate the motor than you are sure that it requires replacement. If the motor works, but nothing happens then the gears or cables are bad in the regulator. Replace the regulator.