Recently, and not all the time, the wiper arms on my car are so weak that they get stuck on the last wipe of a screen wash 'job'. At first I thought it was friction with the window, but I've since tested by holding the wipers away from the window with my hands while the arms try to move it. I can feel with my arms holding the wipers that the wiper's arms are struggling to move the whole thing.
Inexplicably - other times they're fine.
I don't quite know whether it's purely mechanical, or relies on the battery, or involves rubber pulleys. Before I reluctantly take it to a repair garage (where they might quote for an expensive complete system replacement) I thought I might ask here to see if there is any knowledge of how these work in my model of car.