Fixed it!
My horn stopped working this past January.
All the controls on the steering wheel work, radio, etc.
I replaced the clockspring with OEM back in June 2023 and everything worked fine from then to this past January, when horn stopped working.
I swapped out both 10A fuses (one in dash fuse box and one in relay box under the hood) and still no horn.
When I push on the horn I hear a click by the dash fuse box so I assume the horn relay is working.
I have another 4Runner so I swapped out one of the horns with it, and the replacement horn wouldn't work either, but the original horn from 4Runner #1 that I put in the other 4Runner does work, so I feel I ruled out the horns themselves being an issue, at theast the one on the right side that I switched out.
Using a multimeter, I'm not detecting 12V at the horn plug (unplugged, with Pos into the plug and Neg at the neg battery terminal, multimeter set to 20VDC) then the attempt to honk the horn is done at the steering wheel.
And I just replaced the horn relay anyways with new OEM today and still, doesn't work.
Any suggestions? This is a 4th gen BTW, but I'm hoping mods won't delete as their systems are pretty similar and there's way more 5th gens on ther road.
EDIT: FIXED IT!
It ends up that the horn on the left side (when standing in front of the engine and facing in) has two wires feeding in to it. The horn on the right has only one wire feeding into it.
The two wires on the left horn are: one feeding power into the horn connector, then one feeding power back out of the connector and into the horn connector on the right.
In short, the two horns are wired in series and NOT parallel, despite what I read elsewhere, maybe here in T4R somewhere.
Even though we tested the wires for continuity from the relay socket to the connectors to both the left-side and right-side horn connectors and got zero reading, we didn't realize that there were two contacts that we should've tested at the left-side connector. We were about to run a new wire from the relay to the horns when we decided to test for continuity one more time and had the epiphany when I must've touched the second contact while manipulating those wires and got a reading.
From there it was downhill. Simply open up the loom to expose a little more of the wires, cut off the bad connector for the left-side horn and solder on a new 1/4" female flat spade receiver and voila.
We probably could've figured it out if we had a signal tracer and I actually ordered one yesterday but hasn't arrived yet. Oh well. Glad that's over with. It ate up most of my weekend.
So, after 22 yrs of service (it's a 2004 4th gen) , I'm guessing road vibrations (the horns vibrate on their single bolt mounts) caused the input wire to become disconnected in the connector. Not sure if the 5th gen horns are wired the same. If so, hopefully the mods will keep this here since 2030 is just a few yrs away : ).