try replacing the rear wiper blade with one of the new single element blades , not sure of the name but IIRC they may be marketed from Bosh or Rain dance they cost about 20.00 per blade and its one long piece with no extra arms that attach to the extending edges.
I had my whole arm replaced under warranty as the sun seems to melt the plastic and then it looses tension,
The new generation blades may cure this problem

 

try this link
http://www.amazon.com/dp/B000IY8T0Q/...SIN=B000IY8T0Q

 

For me I had this issue for over a year of changing blades. I changed the whole arm last month and fixed the issue. If the top half of the arc is not making contact, your arm is bent or out of tension. If you live in a snowy climate, the snow builds behind the spare tire and puts a lot of weight and torque on that arm. You may be able to adjust the tension but for the minimal cost of a new arm from AB..... I just cut the washer fluid line outside the car and used the appropriate poly ****** fitting to join them back together. Just leave enough length outside the door to do this 2 or 3 more times during the life of your vehicle.

 

stars should read b a r b e d