HOW HORNS WORK
I'm not familiar with your 65 physically, but your horn relay should be under the hood. On my 67 it was originally fed right off the alternator stud, so start there
You are looking for a small metal box with a 3- wire conector
One wire get's LOTS of power a fairly large wire. This feeds one relay contact and one end of the coil (electromagnet)
The "bottom" end of the coil feeds off, through the bulkhead, and when you mash the horn button, it grounds and completes the circuit.
You should be able to reach in through the window while leaning your "ear" under the hood and work the button and hear the relay click. If you cannot, this might be the horn button or wiper contact dirty, or the wire through the bulkhead connector lost connection, or the relay is bad.
(Just because it clicks does NOT mean the relay is good, but at least it does do that)
When the button grounds the coil and pulls in the relay, the main feed wire goes through the relay contacts and feeds to the horn
Download yourself a shop manual, for free here
http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617
More manuals "and stuff" here
http://www.mymopar.com/index.php?pid=31
Also on this same site are simplified wiring diagrams. These are both good and bad. They are sometimes easier to follow than the factory ones, but sometimes incomplete and incorrect
Here:
http://www.mymopar.com/index.php?pid=18
