A couple years ago, my van's horn was working irregularly, and when I turned
the wheel full left or right the horn  would toot on it's own.  Then one day,
it started honking continuously on the road, had to get out and disconnect it
to shut it up.  It was then that I noticed a strip of brass hanging out the
side of the steering wheel.
       The culprit was a worn out contact ring under the steering wheel.  The
brass ring was worn thin, and ripped during a turn, jamming the contact with
the rolled up pieces.  Pull the steering wheel and have a look at the bottom
of it.  BTW, the replacements you will find at junk yards are usually worn
out, too.  I got creative and made my own out of a sheet of brass (a pain in
the brass).  Best of luck.

Bill Marshall
85 GL Tiico
Phoenix AZ