Originally Posted by krane operator

I came to the conclusion that the rear window stops working when i wash the truck or go through drive thru car wash, due to the soaps and wax in the water that trickle their way into the cable.(my theory anyway) Some how it causes a glue like substance and causes the motor to stick(the cable that is wound up inside motor that moves window).Long ago I removed the seat and gave the motor a good tap with a hammer and it started to work. I even went as far as removing the motor and shooting alot of lubricant inside, but still sticks after a couple of months when i dont open and close it often after washes. So this is what i did today and it workd for me. May work for you. Please be careful and this only works in Lariat with fold down armrest. To check if this indeed is your problem your interior lights should dim when hitting the switch to open. This means you have power to motor and its stuck.
Attachment 204181
Locate center of height and width

With fingers press really hard and locate a "bump" . It wil be in center twords the bottom. It will be the only bump. This is the center of the motor.

Right here is bump(center of motor)where sdriver is pointing

Use a hammer to hit the bump dead center, not to hard ,a good whack(not resposible if u brake something. May have to play with it.Motor case is metal and braket it bolts to is metal. At the same time............

Have someone toggle the swith to open as you hit the motor.
Window should open.
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Lube all the cables on both sides of window with lubricant to help the cable. Hope this helps someone. It will also help to open close the window after a carwash so it dont stick. Even a couple of hours later. Remember also to lube cables often.