ML320 Horn (not Security Horn)
 

After an "vigorous" use of the horn (under the front bumper not the security horn) it now goes off randomly and can only be stopped by shutting off the ignition and restarting. I have swapped out relays with no luck. This includes swapping relays while the horn was randomly blowing - any relay inserted caused the horn to continue to blow. No manipulation of horn area on the steering wheel affects/stopped the horn. Help??