Ok - this will work for you.
The voltage regulator is not the one you have now. You will need a new one.
The AC loads will be your lights.
The DC loads can be what you want - like your new horn, and any other DC loads that you want.
Buy this regulator:
http://dratv.stores.yahoo.net/12vorerecoun.html
An this plug:
http://dratv.stores.yahoo.net/12vrerepikea.html
Hope this helps.
