Rick's Free Auto Repair Advice

Test power window regulator

How to Test power window motor and regulator

Before you can replace a broken window regulator, you have to remove the door trim panel and the moisture barrier. See the previous article for complete instructions on how to remove those components. Next, you’ll need to test the system to confirm that the problem is in the regulator itself and not the master switch or the car’s wiring. The test is simple. All you need is a digital multimeter.

Power window motors get their power and their ground from the master switch. The motor only has two wires. The master switch literally toggles the power and ground on those two wires. To power the window down, the master switch provides 12 volts on one wire and ground on the other. To move the window up, it reverses the polarity. Yes, it’s that simple.

Test the window regulator

Disconnect the electrical connector from the regulator motor and reconnect the window switch assembly from the door trim panel to the window wiring connector. Set your multimeter to volts. Connect the red and black probes to the two wires on the connector you just removed. Then turn the ignition key to the RUN position. Toggle the window switch up and down. If the meter reading toggles between +12 volts and -12volts, the switch is good. The problem lies in the window regulator.

Toggle the window switch and check meter to see if it switches from +12volts to -12volts

Toggle the window switch and check meter to see if it switches from +12volts to -12volts

Many of you will ask, “What if the window goes down, but not up?” — or the other way around. The answer is still the same. If the voltage toggles between +12V and -12V, the problem is in the motor or regulator.

If the voltage does NOT toggle, then it can only be two things: Bad switch or broken wire. Wires break most often in the hinge area of the door.

If you need to replace the window regulator, click here for instructions.


© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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