reminds me of that scene from "Little Miss Sunshine"  where the horn  is
intermittantly beeping on the vw bus :)

probably your brass contact ring is worn thru

In a message dated 7/13/2015 9:54:41 A.M. Eastern Daylight Time,
dennisjowell@GMAIL.COM writes:

Help! My  horn is going off when I turn the steering wheel left or right
when parked or  driving.
I took the horn assembly apart, unconnected the +&- leads.  While parked,
ignition on, no horn rim, turned the steering wheel and the horn  blows.
Crazy! Drop,the steering column electrical harness and found no  apparent
problem there. Is there a fix for this?