Using my turn signals turns on my windshield wipers. To complicate matters, I can't turn off the windshield wipers. In the Off position, they continue to wipe. I have to change it to intermittent and then a couple of minutes later I can turn it off and sometimes they stay off. Until I use the turn signals again.

 

Welcome to the wonderful world of the Ford multifunctional switch. I have the same thing happen every once in a while in my 95 ranger. I'll be driving down the street and they just come on or like you said with the turn signal. You have two choices learn to live with it or pop the steering wheel and replace it.