Sounds like the gearbox "thinks" the wiper is all the way to the left when it is actually in the center of travel.
The only other thing I can think of that could do this is the intermittant wipe relay or control box -- if it is bad, it may be cutting the power in the wrong place, or has a wire off.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!