On my 04 f150 the passenger side back door window I replace the whole system 10 months ago, and now the window get down but don't go up any more, I taste for power in the motor connection and is OK,
The motor is bad. It takes more power to lift it than let it down.
Remove the door panel. move the window up far enough so you can sandwich it between the palms of your hands. While lifting have someone depress the up button. If you can feel the motor trying to move the window up you probably have a bad motor. Make sure there is nothing binding the window making the motor work harder.
Search Ford F-150 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Ford F-150 Experts