I am not sure how far they should open, but there is a piece of aluminum or plastic in the window rail, I forget, that keeps them from opening wider. All you need to do is drill out the two rivets that hold the crank in, slide the arm out of the rail in the window and cut the spacer slide everything back together and re rivet the crank in.
I had a window that had the roller out of the rail. Two rivets and five minutes I had it fixed. That is how I realized they are limited with a piece in the rail.
Maybe not a good description but a really simple design.
2011 Ram 1500 Outdoorsman
2014 Rockwood 2909SS Emerald Package