For some reason unknown to me, the rear wiper arm on the Prius II cannot be lifted more than a couple of inches off the glass - and one must hold the arm the entire time it is off the glass. This task makes some common jobs (cleaning the window!) somewhat inconvenient. It appears that this "feature" was a design decision. Fortunately, the feature can be removed, and proper function restored to the spring arm. Remove the cover, remove a plastic tab in the cover, snap back on - and everything works (and still looks!) as it should.

Here is the rear wiper with the cover in place. That plastic cover can be popped of by just pulling under the side edges with your fingers. Pull a bit out (to spread the cover) and up away from the glass.

Here is the cover upside-down on the bench. The two pins you see toward the front, and the smaller tabs toward the rear are what holds the cover on. The rusty pliers are holding the little tab that prevents the wiper arm from pulling away from the glass. That's the little bugger that needs to be removed.

Here is the tab removed, and the resulting cover with the edge trimmed down. To remove that tab, I first cut the two sides with a small Xacto knife, and then just wiggled the tab back and forth to crease it. It will finally break off... then just clean up the cut with your knife to smooth the edges. Of course you should take care NOT to scar the outside of the cover, or scratch it on your bench.

Snap that cover back on, and presto - the arm can be pulled all the way back, and it stays there!