Power Window Regulator Diagnostics – UnderhoodService

Power Window Regulator Diagnostics

Before you start pulling a door panel on a vehicle to replace a window regulator, you might want to start looking at the repair information first. Most power windows are more than just an electric motor and switch that changes polarity.

power window regulatorBefore you start pulling a door panel on a vehicle to replace a window regulator, you might want to start looking at the repair information first. Most power windows are more than just an electric motor and switch that changes polarity. Most late-model regulator and window assemblies have their own controller that does a lot more than just move the window up and down. These can determine the position, speed and current draw of the motor.

Never underestimate the power windows on a vehicle. Skipping to the replacement part of the repair will only result in wasted time.

Uses of a Scan Tool

On most modern vehicles, the windows are tied together with a serial data bus that will connects with the BCM and other modules. With some scan tools, it is possible to view switch commands. This information can be used for diagnosis of the switch and motor. It can also be used to observe commands to the windows when the door is opened or when the remote is used to open all the windows.

Understand Anti-Pinch

Most power window systems have an anti-pinch mechanism that is designed to prevent the window from closing on a passenger, and it controls the express up and down features.

The controller or encoder is part of the motor and regulator assembly, and monitors the current draw, speed of the motor and position. An obstruction is detected by current draw and/or if the movement of the window slows. The control will stop the motors and reverse the movement.

Initializing the Window

If a regulator or motor is replaced, the new part must learn the position of the window before the window will operate normally. If the window is not initialized, the express up or down feature will not work. In some cases, the window will stop before it reaches the fully closed position.

The initialization procedure typically involves moving the window from the full up position to the full down position and holding for a set period of time, but this depends on the make and model of the vehicle.

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To see inductance inside the primary windings, use an amp probe placed around the positive wire for the ignition coil.

Kilovolts or kV is the unit used to measure the output of an ignition coil. Some coils can output 20kV to 40 kV. So, how does an ignition coil turn system or battery voltage into these huge voltages? The answer is inductance. 

The ECM provides the voltage to the primary coil winding. The primary winding might have 100 turns around the coil’s core or plates. When the voltage to the coil is turned off, a magnetic field collapses. The collapsing field will generate more than 100 volts thanks to inductance. The energy is transformed by the windings in the secondary with inductance again, but thanks to the 10,000 windings, the voltage is boosted to 40kV at the spark plug’s electrodes. The best way to see inductance inside the primary windings is to use an amp probe placed around the positive wire for the ignition coil. With this setup, you can see the current ramping in the coil and the collapse of the magnetic field. 

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