 Re: bronco tailgate
Usually the problem is that the gate is not fully closing enough to close the latches completely. (which is why some people replace the rubber grommets..) The gate may look closed, but if anything is wedged in it.. or it's mis alligned even a little.. 1/4" is enough to keep it from operating.
Remember there are 2 safety switches, one is the lever at the bottom of the window seat, to keep you from opening the tailgate while the window is up. 2nd is a contact switch located in the tailgate latch usually on the driver side of the gate. There is a latch on both sides, but only one has the switch in it. when the gate is closed, the bar (on the body) pushes into the latch causing the latch to close and lock around it. The latch must be fully closed to toggle the switch and allow you to roll the window up or down.
open the gate, push the latches closed and see if the window operates. You'll have to pull the handle to open the latches when you're done testing.. make sure the latch is fully open before triing to close the tail gate. and IF you raise the window while the gate is open, remeber unless the window is back down, the gate handle wont open the latches. (safety switch #1)
One other note.. The glass wasnt designed to open while the gate is open and laid down.. If you DO OPEN THE GLASS this way.. have someone support it.. otherwise you'll get some very nasty scrapes on the glass.. (I learned this all first hand). | 
