How do you fix a 1995 Nissan Maxima power window that will not stay up?

The gears are most likely stripped, youll have to take the door panel off and replace them. Or do what I did put the window up and jam a piece of cardboard in the bottom.

I ended up replacing the regulator on both doors. The system is basically a rubber gear bonded to the electric motor, which sits within a nylon gear (kind of looks like a starfish) that runs the window up and down. I tried, unsuccessfully, to epoxy the motor drive-shaft to the rubber gear, but it only lasted a couple of weeks. Finally bought two at a junkyard. They were easy to replace.