I have an early 1999 Jetta III with power windows.  Over the last 18 months or so, I've replaced almost all the window regulators & lift motors.

This spring the rear, driver-side window began itermittently NOT going down.  When it would go down, it would go up with no struggle or binding.  One afternoon last month it would not go up.  I've removed the glass from the regulator and taped it up to prevent rain water entering the car.

The window motor makes no noise... clicking, humming, nothing.  It's like the motor is not getting power. 

- I've replaced the door switch with the one from the other side... no change.
- I've checked the dash switch.  It looks fine.
- I removed/checked the regulator... goes up/down smoothly with no binding.
- I've replaced the motor with a rebuilt one I purchased... no change.
- I've blown/replaced the fuse while working with it... no change.

All the other windows work.  Does each window have a separate relay that might have failed?

Is there a location prone to wire breakage I should check?

Is there a location prone to ground problems I should check?

There are so many wires for the motor... I don't know if I could trace each to see where power is lost.  Does someone have a suggestion?

Thanks for your help,
John.

check the wiring to the door in the b pillar, i think that should have a twist connector and check for broken wires there also

X 2.   I have found damaged wires there before.  You said it didn't ACT like it was getting power?  Is it?  You can usually find wiring diagrams on line.  But, as a rule, red wires are power sources, brown are grounds.

Pull the rubber boot back between the door and the body, they're really bad to break the wires in there going to the door.  IIRC the harness isn't that expensive (or wasn't a few years ago) if you feel like replacing it.