Most modern vehicles have a power window switch located on the inside of the door that allows the driver or passenger to raise or lower the vehicle’s door glass.
How Does a Power Window Switch Work?
Power window switches allow a vehicle’s passengers to open or close the car’s windows. In most vehicles, there are switches on each door, with a master power window switch on the driver’s side that has control over all windows.
Most basic power window systems have switches that allow power to go through to the power window motor when pressed. The direction power runs through to the motor depends on the direction the switch is pressed, which allows for the window to be opened or closed.
Power Window Switch Diagram
Notice that in the basic power window schematic shown here, the switch that controls the passenger side front power window motor is wired in series with the passenger side switch so that, when both switches are at rest, both sides of the motor are grounded. Each power window switch is a “ganged” pair of switches (see dotted line in center of switch connecting the two switches). This means both switch contacts always move together in each switch assembly.
When the pair of switches is moved to the “up” position on the right front switch part of the master switch, the left hand part of the switch makes contact with power in the center, and the right hand side of the switch remains grounded throughout that movement.
When the switch is moved to the “down” position, the right hand switch makes contact with the power in the center of the switch, and the left hand switch contact remains grounded. In the switches themselves, this is done with contact points.
But notice that when the passenger door (right front power window switch) is at rest, the current to the motor flows through the switch to the motor. When the passenger side switch is operated, the same rules apply, except that the ground used by the passenger side switch must first pass through the companion switch in the driver side (master switch).
What that means is that the switch on the passenger door can be inoperative because of a problem with the driver side switch, even if the driver side switch will operate the right front window motor.
On a system wired this way, if you disconnect the power window motor and measure the wires you disconnected from it, both wires leading to the motor should be grounded. If both wires aren’t grounded, the problem could be with either switch or the wiring between the switches. If you don’t find a ground on both sides of the motor, then check the wires leading to the passenger door switch. If both of those are grounded, then you have a bad passenger door switch.
Other Power Window Systems
In more complex systems usually found in modern cars, the power window switches don’t directly send power to the motor. Instead, the switch is connected to electric modules or body control modules located around the vehicle. These modules work like a relay, functioning as an electronically controlled switch.
Early one-touch-down power windows had a dedicated module for that purpose, usually just for the driver’s window. Newer vehicles will use the body computer (BCM) circuits for both one-touch-down and one-touch-up.
Some power window systems (like on mid 2000s Chevy Trail Blazers) have a small microprocessor built into the master switch that must be initialized with a scan tool if that switch assembly is replaced. This means that on the Trail Blazer, the switch isn’t plug and play.
Most window switches are typically made of plastic, with metal wiring and prongs inside. If the internal components get wet enough to saturate the inside of the switch, the water will stay there long enough to corrode and ruin the switch’s functionality.
Faulty Power Window Switch Symptoms
When the power window stops functioning, it may be caused by several faulty components. If the power window switch is at fault, it should exhibit the following symptoms:
The Power Window Motor Doesn’t Draw Power
The quickest way to see if power is making it to the power window motor is to have the door open and the key on, and operate the window switch while watching the dome light. If the dome light dims slightly when you operate the switch, you’ll know power is making it to the motor and that the motor is bound up for some reason.
If the light doesn’t dim, then use the above diagnostic steps to check the switch. You can also disconnect the power window motor and connect a stop lamp bulb (use a socket with the wires) in place of the motor. See if the bulb comes on when you operate the switch both ways. If it does, you’ve eliminated the switch.
If there are no signs of the power window motor drawing power, then the power window switch could be to blame.
The Power Window Can Only Be Controlled by the Master Switch
In certain cases, the window switch located in the passenger door might not work but the door glass can still be raised or lowered using the master switch. In this instance, there is a possibility that the power window switch in the passenger door has failed.
But as stated above, the master switch can be faulty and still operate the passenger side window while not feeding the necessary constant ground to the passenger side switch. This is the reason why it’s best to use troubleshooting procedures for checking the ground and both sides of the motor with both switches at rest.
The Master Switch Can Only Control Select Windows
A faulty master switch might have some circuits that are still functioning while there could be others that don’t. If this is the case, only some of the vehicle’s windows may be opened or closed using the master window switch.
The Switch Works Intermittently
Sometimes, you might need to press the window switch a few times before it works properly. Other times, the switch can open the window but not close it or vice versa. If this is the case, the switch’s internals may have corroded, but it hasn’t caused the switch to lose all of its function yet.
If the window has been left open so that it has rained on the switch enough to get the switch assembly wet on the inside, suspect the switch. Usually, you’ll see chalky deposits on the switch wire terminals in this case.
How Much Does a Replacement Power Window Switch Cost?
A replacement power window switch can cost from $30 to $500. Factors that affect the price include brand, set inclusions, and the intended vehicle model.
Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.