FYI .....just received a Thor recall notice 2018-556 Safety Advisory RC000161 related to windshield wiper system on certain 2013 coaches. Mine happens to be a 2013 ACE 30.1. The recall suggests windshield wiper systems on affected coaches should be inspected by the Dealer. They will troubleshoot the system per Thor requirements and worst case it may result in total replacement of the wiper system. Of course there are no instructions for the customer since there is legal obligation I assume for Thor to sign off on safety recalls.
I have never had a problem with our wiper system (yet) and have driven through a few monsoons in various parts of North America over the years. I have checked them on many occasions based on other coach owners complaining of wiper arm problems in this forum. The only mod I have done was to adapt the wiper arms to take slightly shorter and much cheaper automobile wiper blades....because paying $10 per wiper is better then $50 per wiper.