My 1993 190E uses a single, large wiper blade, and the last few that I've gotten from the local Mercedes dealership have a tendency to squeak. I've tried cleaning the glass and the wiper blade with water and clean cloth, but I can't get rid of the squeak which occurs when the blade travel over the center of the windshield. What is causing this squeak, and how can I get rid of it?

Thanks,

Will