Not a van but a 56 Chevy.  Vacuum powered windshield wipers crapped out
going over the Sierra Nevadas by way of South Lake Tahoe...in  a snow storm.

Rigged a fishing line out one window to the wipers and around through the
other front window.  Grab line, move back and forth and drive.  Worked more
reliably than the vacuum wipers but I think my hand was pretty toasted by
the time I got out of the snow/rain.

Mike