The first step to diagnose a power window problem on a vehicle is to determine whether all of the windows do not work or if just one window does not work. Most automotive electrical systems use a single power supply and relay for all windows. If all windows stop working simultaneously, check for a bad relay or fuse. If all relays and fuses are fine, the next diagnostic step is to check for an accidentally activated master door lockout switch.
If only one window does not roll up or down, it is likely that the door switch, window regulator or power window motor has failed. If no mechanical noise comes from the door when the power window switch is activated, either power is not reaching the motor or the motor is broken. If the motor runs but the window does not work, the clutch or power window regulator are the most likely causes.
To test the electrical current of each door, it may be necessary to remove the door panel of the window in question. At this stage, a trim removal tool and Phillips head screwdriver are necessary. A test meter, such as a voltmeter or ohmmeter, can measure whether power reaches the wiring and if voltage reaches the mechanism when the power window switch is pressed.