My 68 350 coupe has an interesting issue. For no good reason,starting a couple of months ago, when i open the door, the horn goes off and stops when I shut the door, it stops. I disconnected the two horns so I could drive without the horn attracting attention. Quite by accident, when driving at night, I went to hit the horn (forgetting I disconnected them) and the courtesy lights and dome light when on and do any time i hit the horn on the wheel, otherwise the courtesy/dome lights work fine and the car has no other electrical issues. Any thoughts
Henry, I got us all sidetracked here and it seems we're ignoring you sorta. Very sorry...
Here's what I think MIGHT be your problem. Wires on the horn relay could simply be swapped. Check wire colors to a wiring diagram. It just seems to me that if wire #4 was hooked to terminal 1 or 2, and wire 1 or 2 was hooked to terminal 4, and maybe in conjunction with a bad insulator at the drivers door jamb switch...or incorrect wiring at the switch...
I'm thinking some combination of this might do what you describe...
Failing that, I can easily see corrosion or some sort of failure within the horn relay itself sending voltage to places where it shouldn't be sent...like that coil broke and a wire from the coil is now shorting to terminal 2 and/or 4 internally? You might need to replace your horn relay.
