C-280 Uni-Wiper

Dear friends:

I have a 1996 C-280 with a sluggish windshield wiper. It only has one, a Uni-Wiper, I suppose. It runs at normal speed for the first 1/4 and last 1/4 of the sweep, but seems to "bind up" when it has to retract, and runs REAL slow through that portion of the cycle. This is temperature sensitive, as this morning when it was 60 it worked fine, tonight when it is 30, YEECH.

How do I access the operating mechinism? What do I lubricate it with?

Thank you,

Chuck