Horn Works When Key Off but Not When On
 

1999 Boxster. My horn stopped working a couple of weeks ago. It works fine if the key is off but won't work when the key is turned. Fuse is OK. I know there a lots of issues with the horn but this is the first one like this.

Any advice?

This is like the fourth post on this in the past week. Check the other posts, there has been some discussion on the topic...

-Wayne