My 96 did the same thing. Turned out to be the turn signal switch assembly. I had it a part and found that the handle mechanism can where out the brass connector tracks causing it touch just enough to activate the system, but not activate the turn signals themselves. Anyway, the solution is to replace the whole assembly. Take the top cover off of the steering column and release the top of the turn signal assembly (it has one of those locking thingy's, you'll see it) as you lift unplug the 2 harnesses. Put new one in.
10 min job, tops.
I paid 25.00 @ junkyard or go to fordpartsonline.com they have them for 75.00
