Wow great thread here that Im going to follow. I have a 68 RS rewired by PO with American Autowire. It had no horns on car when I bought it, but bought an aftermarket set of high/low horns that someone on this site recommended as an alternative. Currently working on replacing/tuning dizzy and carb, but will venture out in my spare time to look into horns again.
Quick question if I may ask, my horn relay is up in the dash behind the speedo (AAW), I tested the circuit by putting a test light in the plugs on the radiator support and they lit up when I pressed the horn button on steering wheel. Would this indicate my button/relay circuit is working correctly? I tried hooking up the horns and they still didnt work. I understand it may a ground circuit issue that maybe something to check out.
Following for helpful info.