I had a similar problem in my 87, my horn would intermittently sound when I
would turn the wheel or use the turn signals.  The problem was that the turn
signal/wiper switch assy. was loose and shorting to the horn.  To check to
see if this is your problem remove the steering wheel (be sure to note the
orientation of the wheel so you can line it up correctly when you put it
back on), then check the two brass screws at the top of the turn signal/
wiper switch assy.  Tighten if loose and reinstall the steering wheel.

dave
www.251.org