Okay, I've been troubleshooting my passenger side front window which stopped working a few months ago.

Here is where I'm at-

Voltage at the switch.
Tried hooking up a known working switch.
Voltage at the motor on the door when switch is applied.
Greased the rails.

Still does not move at all. Up or down.

So if I'm getting power at the motor, does that mean the motor is shot?

Thanks!
-Ryan

How did you test for voltage on the door?

I took off the door panel. Peeled back the plastic sheet. Unhooked the cover for the terminals at the window motor. Hooked up my multimeter to the two terminals at the window motor. Then I hit the window switch. I read voltage.

Did you try the window switch in both directions?

If so, you'd see the meter try to go to less than zero due to the polarity error.

If you found this to be the situation, then your testing procedure is valid and the motor is NG.

I don't recall if I tried it in both directions. I believe I did, but I will try it again when I have time, probably not until Friday evening.

When you say 'try to go to less than zero' I'm assuming you are talking about an analog multimeter? I know your feelings on digital ones but if using a digital shouldn't it register negative then? I do have both an analog and digital one.

Thanks for the help.

When you applied power to the motor can you feel the motor trying to do anything? Tell us what car this is. On my 83 I found one of the bearings frozen on the motor shaft in the front passanger side and after taking it apart and cleaning and lubing it works fine. Also the brushes could be sticking.
On this post I have some pictures of my window motor when it was all apart.

Replacing window motor?

__________________
1983 300SD
200000miles

Yes, an analog meter.

Correct, I'm not fond of digital meters............the performance of the meter would be dependent on the model. I presume that the meter would read a negative value for voltage in that situation.

Phil,
The car I am working on is the one by my name. It is the 84 300SD. Thanks for the link.
No, it didn't feel like anything at all was happening when I pressed the switch.

I guess I will first try the switch in both directions as Brian stated to see if it goes negative in one direction. If this happens then I will take the motor out and clean and lube it to see if I get any improvement.

Thanks for your help.

On mine the motor didn't move but if I had my hand on it when I applied power you could feel the vibration like it was trying to turn but couldn't.
In the photos you can see the brush holder and if you get into it that far you could check if one or both brushes are stuck and not making good contact with the armature.

__________________
1983 300SD
200000miles