Windshield wiper problem!

I have a 1991 Aerostar with @110,000 miles on it. My problem is this. When driving, especially when windy the windshield wipers somehow lift a little bit and then just start working on their own. The switch is still off, but the wipers keep going. Nothing makes them stop either unless I turn the ignition off. They work fine manually on the low and high settings, however the intermittent settings do not work at all?
Anyone come across something like this?

did you get any replies from your question or did you fix the problem? I also have the same problem.

i would be interested to,my problem is only low&high
work but not intermittent unless iuse the turn signal
or turn the wheel(clock spring?).