I can hear the motor trying to move the wiper blade. Often I can hit the **** with my fist a few times when I hear the motor turning and the wiper will begin working. It will work until I open the liftgate or the window, then I have to do it all over again. At least I hear the wiper motor running which tells me it could be a worn gear inside there or some slippage at the arm inside the rear door.
Does anyone know how to access the wiper motor by taking off the trim inside the liftgate?

 

Do not do this! the reason your wiper is not getting past the glass edge is because it's getting caught on that glass edge! The reason it starts working when you hit it with your fist as you're giving it the bump it needs to jump over the glass edge and onto the glass the reason it stops working when you open the lift gate window is because there's a switch in there that tells it to stop working when you open your liftgate window so that you don't accidentally have your wiper smack you in the face or arm when you're taking things in and out to the liftgate window. to remedy grab the Little foot sticking off the bottom of the wiper arm and pull it towards you with your left hand GENTLY while holding your right hand on the end of the wiper arm that holds the wiper. Check functionality. Still getting stuck? Pull it a bit more. If still getting stuck repeat repeat process up to two to three more times pulling gently a little bit more every time eventually you'll get to the point where you've pulled too far and it'll not only clear the glass but it will not be touching the glass to reverse simply push in on the foot instead of pulling out until you meet the happy medium. Voila!