I have a 94 E420 that has a single wiper. The wiper works well but it makes this ticking noise. The wiper would swing all the way to the passenger side, and just as soon as it changes direction (comes back to the driver side), it makes this ticking noise (when the wiper is pointing at 2am or so). I can not figure out what it could be but it's very, very annoying! It's not the rubber squeaking against the windsheild. It sounds like the arm is rubbing against something - it's a ticking noise that's pretty loud.