Diagnose power window problems

Diagnose power window problems — window goes down but not up

Car window problems can be electrical; either a bad switch, bad wiring or a bad power window motor. Or, they can be mechanical; broken lift cable, broken lift tape, broken idler roller, broken sash clip or a binding window channel.

Diagnose car power window problems by symptom

Symptom #1 Window goes down but not up or window goes up but not down

Power windows work by supplying power and ground to the window motor and then reversing the power and ground to make it go the opposite way. This all happens in the master switch on the driver’s door, or, on late model vehicles,  it happens in the window controller. In those vehicles, the door switches don’t actually switch power to the window motors, they just act as inputs to the window controller; it’s the controller that toggles the power and ground.

So here are the possibilities of a window that only works in one direction:

Bad master switch. It’s almost always the driver’s master switch because it’s used most often and gets wet most often. The copper contacts inside the switch get corroded and may work the window in one direction but not the other.

Wiring harness/connector issue. This happens more often when a passenger or rear seat switch causes the window to only work in one direction. If it’s a passenger or rear seat switch that causes the one-way operation but the master switch work properly, it’s either a bad passenger or rear seat switch or a wiring harness/connector issue.

Dead spot on the window motor. A dead spot on the motor armature can cause the window motor to not work. Somtimes you can spot a dead spot by banging on the door to jar the motor a bit. If a good smack makes it work, suspect a bad window motor.

Symptom #2 —You have to press the window switch multiple times to make window go up or down

This is usually caused by a worn or corroded switch. However, in some rare cases, it can be caused by a worn spot on the window motor armature. If you press the window switch multiple times and the car window won’t go up or down, smack the door panel hard with your fist. If the window motor operates after a good smack, that’s the sign of a bad motor or a problem with the wiring harness or connector inside the door. Time to remove the door panel and check out the wiring.

Symptom #3 — Power window is slow to move up or down

A slow moving window is often caused by dirt buildup in the window channels. The easiest way to diagnose that problem is to lubricate the channels. Use either silicone spray or Dry Teflon Lube. The advantage of dry Teflon lube is that the slippery particles don’t attract dust and dirt like wet silicone. However, the dry Teflon powder turns white after the solvent evaporates and some people don’t like that look. Whichever you choose, aim the nozzle straw directly into the window channels and saturate the front and rear channels.

Lubricate glass channels with silicone or dry teflon lube spray

If you use silicone spray, operate the window up and down right away to spread the silicone along the channel. If you used dry Teflon lube, wait a few minutes for the solvent to evaporate before operating the window. If the lube helps the window move faster, you’ve solved the problem. If not, the problem can be caused by a sticky or worn window tape, binding cable or worn motor. That requires you to remove the door panel and check out the window regulator operation.

Symptom #4 — Car window clicks when rolling up or down

Clicking is caused by debris in the window channels or failing moving parts in the window regulator. Don’t ignore this problem. It will not fix itself and the clicking will get worse to the point where it can bind the glass and cause it to shatter.

Symptom #5 — Car window won’t stay up or is crooked

This is always a sign that you’ve got broken parts inside the door. The glass window is connected to the window regulator by plastic sash clips. When a sash clip breaks, the window will cock and move up and down in a crooked fashion. You can remove and replace the sash clips but that requires special glue.

This problem can also be caused by a broken window regulator. In that case you’ll have to remove the old unit and install a new one.

How to diagnose a power window issue

Start by checking for power and ground at the motor connector

Power window motors are pretty simple devices. They usually only have two wires. The switch provides power and ground to make the motor operate in one direction. If you see more than two wires, you’ve got a window motor that’s equipped with auto up/down and anti-pinch features. When you operate the switch in the opposite direction, it switches power and ground to the opposite wires. Here’s the bottom line; testing right at the power window motor connector is the best way to diagnose the problem.

Get a voltmeter. Remove the door panel and vapor barrier. Disconnect the electrical connector to the power window motor. Set your meter and 20-volts DC and connect the red and black leads to the electrical connector. Turn the car key to the RUN position and operate the window switch. You should see either +12-volts or -12-volts on your meter. When you move the switch in the opposite direction, you should see -12-volts and +12-volts. If you get those readings, the switch and wiring are good and the problem is with the motor or the mechanical system.

To narrow it down further, reconnect the electrical connector and operate the window motor. Look for any signs of binding or broken parts. If the motor doesn’t move at all, replace the entire window regulator. Trust me on this, it never pays to replace just the motor.

&©, 2019 Rick Muscoplat