They have sold me at Advance Auto twice the wrong size wiper. Now I have the right size also from Advance Auto but the wiper still stops sometimes not as bad as it did with the wrong size ones. The mechanic said the relay is fine it needs a new motor but I took the wiper off and it goes back and forth fine. Could the wiper be getting stuck because it isn‘t made for a Mercedes and should I try before spending $125.00 a wiper ordered from Mercedes dealership?
Try tightening the nut that holds the wiper arm onto the wiper transmission (It will probably be under a little cover). It sounds more like an issue of either not enough motor torque or more likely slippage.
I would definitely get it from the dealership if you can afford it. It will eliminate the hassle of what you have already went through. To me, that has always been worth the extra price.
