When I run across a Williams wiper unit (stepping unit) that is sluggish,
sticky, or frozen, often the problem is that someone oiled the ratchet
spindles. Over time the oil collects dirt and creates a very tough glue
that makes removing and cleaning the ratchet seem impossible. Use a solvent
like Wildcat #125, or alcohol. Wildcat seems to work best on this type of
problem. Work the ratchet back and forth until in loosens up enough that
you can remove it. Pay close attention to all the springs, clips, washers,
and other ratchet pieces you may have to remove to get the one off that has
the problem, so you can get them all back together again in the right order.
With the ratchet removed, use a solvent soaked Q-tip to clean out the inside
of the ratchet and a rag with solvent to clean the spindle. Once cleaned
and reassembled you'll be surprised how easily the ratchet rotates.
Again--never oil these pieces--they just don't need it.