Passenger side window quit in down position in 1999 Ford F150 Lariat. How can I tell if the problem is the switch or the motor?

 

Well will the switch on the drivers door make it go up/down?

 

It's usually a bad switch, motor, or a faulty wiring circuit along the door switch and motor. To find out the cause, you can actually pop out the switch from the door panel (be careful no to scratch it, you can use a knife to loosen it). If it doesn't, you'll probably have to remove the entire door panel. Once you have the switch out, you can use a voltmeter to check for voltage when the ignition is on. If the switch is getting voltage, but the door motor doesn’t move when it's turned on, then it could be a bad switch or motor. Hope this bit of info helps.

 

Neither switch will operate the window. Dome light dims when switches are used. I changed out the motor; still no improvement. At least I was able to pull the window shut by hand. I'll try the voltmeter. Thanks

 

If the lights dim when you hit the switch then the electrical system is sensing you hitting the switch.

Pull the motor and hit the switch with the motor in your hand and see if it works while not connected to the window system. It could be an issue with the tracks not the motor.