Rick's Free Auto Repair Advice

Power window doesn’t work

When your power window doesn’t work, here’s what to check

If you press the window switch and your power window doesn’t work, most DIYers automatically suspect a bad power window motor. That’s usually not the case. Power window motors rarely fail. The switches and the regulator are the most common causes when a power window doesn’t work.

Check the lockout switch first

Most vehicles have a lockout switch on the master switch to prevent passenger windows from opening if the driver locks them out. If your passenger windows don’t work, double check to make sure you don’t have the lockout switch turned on. If the switch isn’t set to the lockout position, then proceed with the diagnostic steps below.

Power window doesn’t work — Symptom: The window goes down but not up or vice versa

If a power window goes down but not up or up but not down, the glass movement confirms that the motor is getting power and ground, at least in one direction. So the problem is not the motor!

Failure in one direction is almost ALWAYS caused by a bad master switch!. It the switch that It’s usually the sign of a bad power window switch.

How to diagnose a power window problem

If you want to fix your power window you MUST understand there TWO CONCEPTS:

First: On all older vehicles, ALL the wiring for ALL the windows runs through the master switch. When passenger windows don’t work, but the driver’s window does, chances are high that you’ve got a bad master switch in the driver’s door or a broken wire in the driver’s door hinge area.

That’s not the case on newer vehicles, however. On late model vehicles the door switches don’t actually switch power to the window motors. They’re just a signal request to the body control module (BCM) to open or close a window. In some vehicles, the BCM provides power to the window motors. In other vehicles, the BCM receives the window open/close request from the switch and then sends a digital signal to a smart junction box and a relay in the junction box switches power to the window motor.

It’s important to know which system you have and that’s where a shop manual is useful.

Second: Power window motors usually only have two wires. When you operate the down cycle on your power window switch, it provides + power and – ground to the power window motor. When you operate the up cycle, the switch reverses the polarity on those same two wires. So if the motor works in one direction just fine, but not in the other direction it’s almost NEVER the motor—it’s the switch.

However, in late models vehicles with a “anti-pinch” and partial ventilate (window moves down about 1″ for ventilation) features, the motor has extra wires to operate these features.

How to test a power window motor

Disconnect the electrical connector from the regulator motor. Set your multimeter to DC volts. Connect the red and black probes to the two wires on the wiring harness 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.

power window doesn't work: test procedure for the motor

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

Power window voltage toggles but window doesn’t move

If you’re seeing the toggling voltage, the problem is in the window regulator. It’s either a bad motor or a broken regulator that’s causing the motor to stall. Reconnect the electrical connector to the motor and try operating the window. If the motor is good, you should see some movement or hear some noise coming from the motor. If you see movement, the regulator is usually at fault. If you have a cable operated regulator, replace the entire regulator.

If the motor shows no movement, it’s probably bad. But again, if it’s a cable regulator, replace the entire window regulator.

No voltage or ground at power window motor

If you don’t see voltage and ground at the power window electrical connector, the problem is either the master switch or a wiring harness issue. Grab a wiring diagram and check for power and ground coming into the master switch. If you don’t see power and ground, head for the wire bundle in the driver’s door hinge area. Since that door is used most often, those are the wires most likely to break due to the constant flexing. If you find an open or chaffing, repair the wire and you should be back in business.

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



Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN