ower windows have become standard in all vehicles, but like all electrical circuits, they can fail. So power window wiring is necessary in such a situation to replace or repair the damaged section.
Let’s analyze this car door circuit to see how it works and its wiring steps.
Table of Contents
How a Power Window Works
Power windows have two primary components.
Lifting/Lowering Mechanism
Power windows operate on the principle of voltage reversal or reverse polarity to lift and lower the window.
This lifting/lowering mechanism requires an electric motor, a worm gear, and spur gears.
The driver motor attaches to the worm gear, which then connects to several spur gears to reduce the rotation speed while increasing torque.
This gear system gives the system enough energy to lift the window.
A power window control motor and gears assembly
The gears also have another purpose. For safety purposes, no one should be able to force the window down by pushing it from the outside.
The worm gear features a self-locking mechanism created by the contact angle between the gear and the worm.
So the worm can spin the gear when the window motor runs, but the spur cannot rotate the worm.
The angled contact between the gear and worm teeth binds them due to the generated friction.
Wiring and Switches
Power windows can have simple or advanced control circuits.
Simple Window Switch Wiring Circuit
Basic systems usually have the power fed to the driver’s door power window switch via a 20-amp circuit breaker.
From this control panel, the power goes to a center contact point for all four door windows.
There are two contact points on either side, and all rest when connected to the ground.
When you press the switch, one of these contacts gets disconnected from the ground and touches the center point.
The other window switch remains grounded, so the power window motor won’t start.
A technician repairing power window wiring in a vehicle
Once it touches the center point, the connection creates a channel that transfers power to the motor, which lifts the window.
Pressing the switch in the opposite direction reverses the electric current running through the window motor, which lowers the window.
Advanced Window Switch Wiring Circuit
Modern cars don’t feed power directly to the electric switch. Since these vehicles have power-lock, power window, power seat, and power mirror controls on the door, you would need too many wire harnesses channeled to the car door.
This wiring would be messy and heavy.
Multiple vehicle control buttons on the car door
The solution is to use a central electronic module known as the body control module.
So the driver switch control only sends signals to the body controller, which then powers the respective window motor to lift/lower the specific door window.
Passenger switches can also utilize this module by sending data packets via the communication bus to the controller, which powers that electric window motor.
A vehicle’s body control module
Power Window Wiring Steps
You’ll need the following components to get the power window system running.
- Power window bi-directional motor
- Toggle switch
- Wire nuts/caps
- Wire stripper
- A red/hot wire (16 to 18-gauge wire)
- A yellow wire (ground wire)
- Jump starter
- 20-amp inline fuse
Step 1: Test the Window Motor
Before wiring the system, check if the motor is working. You can bypass the protection circuit wires to carry out this test while the window motor is still attached to the door.
Begin by disconnecting the motor from the electrical system, then connect it to a 12-volt battery or jump starter.
Ensure the alligator clips don’t come into contact to avoid electrical shock.
The wiring harness for a car’s power window motor
Remember to connect the motor’s negative terminal to the negative side of the jump starter or car battery.
Similarly, link the motor’s positive terminal to the positive side of the battery power source.
The motor should lift the window. If it does, switch the polarities.
The window should go down. These results indicate the window motor is fully functional.
Step 2: Connect the Window Motor
If the electric motor has no wires, connect the red wire to its positive terminal and the yellow wire to its negative terminal.
And even if it has wires, attach pigtails to the existing cables to lengthen them.
Use the wire stripper to remove about an inch of the insulation layer to make these connections.
With the pigtails, you can nest the twisted joints in wire nuts.
Step 3: Wire the Toggle Switch
Next, connect the positive and negative wires from the motor to the toggle switch poles.
If the switch has white and black wires, link the white wire to the positive wire (red) and the black wire to the negative wire (yellow).
Car power window switches
Step 4: Connect the 20-amp Inline Fuse
This circuit needs a fuse for protection from electrical faults like power surges.
Connect the inline fuse to the positive wire linking the toggle switch to the positive terminal on the car battery.
You can insulate the joints using duct tape, but we recommend using heat shrink tubing.
Step 5: Link the System to the 12-Volt Battery
Connect the white and black wires from the toggle switch to the power source to supply battery voltage and grounding to the motor.
After that, test the toggle switch and its effect on the power window. Flipping it to one side (on position) should lift the window.
And reversing the flip (off position) should lower the window.
Advanced Power Window Features
Newer cars have sophisticated power window systems that can have the following features.
Automatic Up/Down
This feature eliminates the need to hold the window switch if lifting/lowering the window fully up/down.
You only have to tap and release the window switch, then let it do the magic.
The explanation behind this operation is a circuit that monitors the time taken to hold the switch.
If held for less than half a second, the control module will power the motor to get the window fully up or down.
But if you press the switch for more than half a second, the control module will only energize the motor when in contact.
However, a challenge emerges when using this system. What if an object, such as a hand or baby’s head, gets in the way as the window rolls up?
Automakers solved this issue using a circuit that checks the motor speed. If it slows, the circuit reverses or stops the motor.
Exterior Window Control
Some German cars allow you to lower the power windows by inserting the car key into the driver’s door and holding it when turned.
The driver’s door module checks the door lock wiring switch and lowers the windows if the key persists in that position past the set amount of time.
A power window mechanism viewed from the outside
Courtesy Power On
Most vehicles keep the power window switches energized after you turn off the car to enable you to roll up the windows without inserting the key back in the ignition switch.
A relay usually powers the electric window circuit for about a minute after turning the car off. So if you forget to roll them up, you have some time to lock up.
Wrap Up
Power windows are some of the most critical car systems because they can compromise your vehicle’s safety if they fail when you park.
And wiring them is not challenging, especially if the car has a body controller in the door. So follow the steps above to get the system running.
Contact us for further guidance if you encounter technical challenges when wiring.
