Time to get the horn working.   That means adding a relay.  Which I have ready to go.

So here is the plan.  I will tie the existing power line on the horn to the relay coil (86-white wire) and the power terminal (30-blue wire).  The normally closed terminal (87a-red wire) will be removed entirely.  The normally open terminal (87 yellow) will tie to the horn power lead.  The other side of the coil will be tied to the horn button.  When the button is pressed the coil will get ground and activate the relay.  Then the horn will go beep.

I cut the existing wiring harness off about three inches down and put a terminal on the end.  This will be the new ground wire for the horn.

Here is the ground wire fully assembled in the factory connector.

Here is the relay.  It has a built-in mounting tab.  There are some existing holes in the fender and this screw fits them.  But the hole in the mounting tab is too small.  But I have a drill press…

Cool.  Now I have to put the phone down and do some soldering…

Like this.  This terrible photo shows the two power wires soldered to the power lead for the horn.  The heat shrink to cover the splice is pushed up out of the way.

And here is the finished result.  Looks pretty neat if I do say so myself.  And here is the final result: