My 99 Deville rear passanger window wont go down by the switch or the switch on the drivers side door. All 3 other windows go up and down fine.

 

When you say drivers side do you mean the rear drivers side switch? If not try that switch on the passenger door, I think they plug in to each other. This will isolate the switch.

Also try this, I know it sounds bad, slam the door real hard, then try the switch, sometimes the motor gets stuck.

Lastly check motor for power to contacts, if yes motor is probably no good.

All windows share same maxi fuse so not a fuse.

 

My bad I should have said drivers door front. I cant even put down the rear window with the drivers switch or the switch at that actual door itself.

 

05 Deville in which the left rear passengers window ONLY works with the doors open(either one or both). When shut.......nothing. How is this possible? lol! WOW! Thanks, Kevin