Is the glass wet? Not trying to be funny... Some motors aren't strong enough to sweep dry glass.... Even some electric ones. If they can't finish the sweep, the arm won't go 'around the horn' to do the return. Have you tried removing the arms and checking the motion of the mounts?
Current fleet (subject to change w/o notice) \'49 GMC 3/4-Ton , 60 Austin Healey Frog-eye Sprite (some assembly required), 2011 Dodge Avenger, 2015 Jeep Cherokee. No, they don't all run. My other ride is a (B737)no, (B767)no, A320.... Update... was Embraer E190, now Boeing B787. Knowledge is a wonderful thing, but ignorance means you don't know you can't do something.
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