If you have a low end car (like my ’77 wagon), they only come with one horn.
You can make a jumper or find a used 5th Ave, get the jumper and the second horn (and its bolt) and presto, you now have two horns (twice as horny?).
Thank you Jim of the great photo of an F-body!
(M-body will be close in appearance, just not as visible as Jim’s picture, sense these parts are behind the header panel/grill)
The main horn wire (blue circle - leading to the blue X) connects to the horn, on a single horn system (much like how my ’77 wagon was built).
Dual horn systems use a jumper (yellow) that plug into the main horn wire (blue), which then splits off going to each horn.
IF you going to go back with factory horns (easier to obtain) and currently have a single horn system, then find a car with both horns. Grab the passenger side horn, its bolt (top) and that jumper (yellow).
Go to your car, plug in the jumper first, then bolt horn in – and test (before you put tools away).
The Lo and Hi horns are marked “Lo” and Hi”, as well rotate in a different direction.
Thank you, Jim, for providing the photo!
The only thing I don’t know is what the mystery wire is for (the purple circle).
BudW