It is a 73, stock engine, tranny, dash, wiring. It looks like the wiring has been redone maybe 20 years ago based on the vehicle history.
The wires don't look in bad shape, connections are tight, it looks a bit disorganized, hard to follow where everything goes.
What makes you think it was redone? Records showing a rebuild or something like that? Are they still factory colors? Maybe they were just gone through and fixed a few flaws, rather than replacing.
When I press the horn button there is a clicking noise from the horn but that's it. Oddly there are two horn speakers under the hood, both wired.
Not too odd, since even though yours is before Ford offered them (first time in '76 I think?) a lot of people would add another horn so that we could play with the grownups back then. Most vehicles of the era had two horns, while Broncos got one relatively anemic one.
So having two is a good thing, but it wears out the horn contacts under the steering wheel much quicker.
Your '73 most likely does NOT have a horn relay, so the clicking you're hearing is either the horns have worn out/rusted inside, the horn button contacts need renewing, the ground at the horn itself is not sufficient, or something else is keeping the full current from making it to the horns.
Easiest way to verify the first half of that is to run a jumper wire straight to each horn wire. With the horn still bolted to the body, a jumper wire will make a good horn honk very easily.
Check to see if you have one or two wires. Factory horns were single wire and the ground was through the mounting bolt. If your Bronco has been re-painted and/or is a bit rusty, you might not be getting a good ground to the horn.
If they honk, you can then move up the chain of command and find out what else is causing the problem.
With the old system the full current to the horn passed up into the column on one wire, then through the copper/brass/whatevertheyremadeof contacts and then down another wire to the horns. All that current flow, especially doubled with two horns, wears out the contacts. You can sand them smooth of carbon buildup, grease them up with dielectric grease and they may be good for a few months to a few years, but the best way to get the horns to work better and the button to last longer is to install a horn relay.
The stereo was fine until I drove on a rough road and rattled the hell out of everything.
No, it is a recently installed, new stereo
Well there's your problem right there. And only you'll be able to find out what came loose, or which fuse blew.
A new aftermarket radio might have it's own inline fuses, and might no longer use the one in the fuse panel. But you might as well check all the fuses anyway, just to rule it out.
As with any vehicle this age using glass fuses, remove them all, clean them, then put them back in. Gives the electricity a fighting chance of making it through the system unmolested.
Then just go on the hunt for loose, or broken wires which only you will be able to find. Could be as simple as reaching under and moving wires around until it works. Or it could be the way you spend the next few days of your life on your back with your neck twisted into an "S" shape under the dash!%)
I put the tire pressure (33") back down to 35 to soften the ride.
Wow! Down to 35? What were you running before?
Most of us are down in the 25-30 range at the most. But that does not mean that yours is not the best at 35 of course. Just that it's still higher than most.
What tire and wheel combo are you running? What is the max pressure rating on the side of the tire? And finally, how is your tire wear?
On the rear tires you can easily see if they have more pressure than needed by looking at the point where dirt is on the center of the tread and where it stops. Where it stops is usually where the tire tread is not touching the ground. Or not touching as much.
The trick is to lower the pressure until the dirt/wear pattern is right out to the edge of the tread, but not further around the edge. This is just about perfect for this load. If you regularly carry a heavy load, then by all means leave a little extra pressure in the tires as a safety practice. But if not, leave it running all the way out to the end of the tread.
Very curious about your setup. If 35 is your proper go-to pressure, love to know more about your tire combination. We're always hunting down information on each other's tire pressures and conditions.
Thanks
Paul