Ever since new, my coach has never made a clean swipe of the windshield. Living in California, we've only had to use the wipers on two occasions in 3.5 years, so it has never been a big issue. However, I would like them to work correctly.
Mine lay horizontal with the pivoting ends at the left and right outer edge of the windshield. In the photo below, the green area does not wipe cleanly. It doesn't chatter, just won't give a clean wipe.
Here's what I've done to date.....I replaced both 36" wipers with new blades and got the same result. It should be noted that the passenger side with the 36" blades always wiped cleanly.
I found that the passenger "blade" was perpendicular to the glass and the driver's side was at a slight angle. I bent the arm to make the driver's side perpendicular, no help. My dealers' service department recommended that I put more of a bend in the arm, adding some pressure to the wiper blade. That made no difference.
I never cared for the fragility of the wiper arms with the 36" blades and changed them two months ago to 32". They swipe a path that's higher than my view out the windshield, so they work well in that aspect. However, I'm still getting a swipe that misses the lower corners, now on both sides.
The wiper arms have large springs that hold the arm against the glass. I guess they could be weak, but this has been an issue since new.
If someone has had the same issue on their Newmar with the same wiper setup, and found a fix, I'm all ears. My next step will be to add some sort of airfoil or wing to the blades to force them against the windshield while moving.