Strong smell of hot insulation from wiper motor may indicate
water has rusted the shaft that moves the blade solid.
You can, with difficulty, get it apart. Re-greased everything
and in spite of the smell wipers fine for 2 years until I disposed
of the vehicle.  Other problem may be phosphor bronze spring
contacts, 3 of them, working on tracks on main gear wheel,
the one turned by the worm. One finger may have lost its
tension, usually the one nearer the gears shaft. A slight bend
to increase contact pressure and all is well again. One big
problem was freeing the stainless bolts retaining the wiper
assy. the diecast threads had corroded and frozen the bolts
solid.