Fix car window won’t go down problem
If you have power windows and experience issues where the car window won’t go down or goes down and then won’t go back up, here’s what to check.
Car Window Won’t Go Down Is Usually a Bad Driver’s Door Master Switch
Why that switch? Because it the one that’s used most often. Because the driver’s window is opened more often, it wears out faster. Plus, the driver’s master switch is exposed to the elements; snow, rain, coffee, etc.
If your windows won’t go down, start by checking the master switch and window motor wiring. However, it can sometimes be caused by a broken sash clip or binding in the window track that’s causing a mechanical issue rather than an electrical problem.
Where to start when diagnosing a car window won’t go down problem
If a passenger window switch won’t make the window go down, try using the master switch on the driver’s door. If neither switch operates the window and you don’t see any window movement at all or hear any motor noise, don’t assume you’ve got a bad window motor. Switches fail more often than window motors. And, if the motor operates the window in one direction but not the other, that’s usually a switch issue, not the motor itself.
If none of the car windows opearate start your diagnostics by checking the power window fuse or circuit breaker. Power window motors usually have a built-in circuit breaker to prevent the motor from starting on fire, so if the fuse is blown, chances are you’ve got a wire short and not a bad motor. If the fuse is good, remove the door panel so you can check for power at the window motor connector.
How to test a power window switch
Here’s the deal with testing a power window switch; it’s impossible
to do without a wiring diagram, especially on the master switch. In older vehicles, ALL the power and grounds for each window go through the master switch. On newer cars where the windows are controlled by the body control module (BCM), the master and door switches send DIGITAL commands to the BCM and the BCM switches power to the motors. On still other late model vehicles, the switches send a digital command directly to the door switch for the passenger windows and that switch sends power to the motor. In other words, it’s complicated. So, unless you have a wiring diagram, start by testing right at the window motor.
How to test a power window motor
Power window motors are pretty simple—they only have two wires. The window switch supplies battery voltage on one wire and ground on the other. When you reverse window direction, the polarity on the wires switches. To test the switch operation set your digital voltmeter to 20 volts or less DC. Place the positive test lead in one connector cavity and the negative lead in the other cavity and operate the switch up and down. If you get a reading in one direction but not the other, chances are you’ve got a master switch problem. Why? Because in most cars where the windows aren’t controlled by a computer, the power and ground for each window flows through the master switch. Don’t get fooled here; the master switch can provide power and ground for three windows but not the fourth. So your next step is to remove the master switch from the driver’s door and test the wires going to the problem window.
If you get a toggled voltage reading, then check for signs of a broken sash clip or binding window tracks. Sash clips connect the glass to the window regulator. When a sash clip breaks the glass can jamb and bind. In worst cases that binding can bend the window tracks and even break a regulator cable. You can’t repair a cable style window regulator, so don’t even try. A new regulator with motor costs less than $100 from any auto parts store.
See this post for more information on how to diagnose and fix a car window won’t go down issue.
©, 2016 Rick Muscoplat
Posted on by Rick Muscoplat