Replace the ww fuse. Doing this solved a similiar problem in my '82 240D. We only find out if the ww don't work when it's raining cause we RARELY use them when it's not raining.
hope this solves the problem.
1982 240D 313,000 (4 speed)
1984 300CD 172,483
1985 German Shepherd Dog -Lacey- R.I.P.11/04/05
Hood Stars, Wrist Crowns and Obsession Dobs