Horn Troubleshooting: Solved!
Wanted to bring one of these "horn not working" threads back to life...
On my 1998 3.0L Ranger, the horns hide underneath the fender under the battery, you can't see them from the top or the bottom, there is a single nut that holds a bracket with both horns attached to it to the bottom of the fender, right between the driver headlight and the battery. When mounted, you can just barely see the positive lead that runs into the main wiring harness along the radiator support.
When mine stopped, the first thing I did was add WD-40, jiggle the wires. It magically works again for 2 months.
It stopped again, gave it the same treatment: nothing. So, I disconnected the wires gave it a more thorough cleaning and inspection, connector looked okay, but still no horn.
I tried both the fuse and the relay, which on the 1998 are under the hood, number 10, a 15 amp fuse, and number 7, a 5 prong relay. When both are in place there is an audible 'click' at the relay when the horn button is pressed, when either one is removed, the click ceases. If the relay is replaced with a known good one, the click is the same, still no horn. This leads me to believe that both the fuse and the relay are good.
Using a piece of speaker wire, I wire the positive lead of the horn direct to the positive battery terminal, upon contact I get an immediate and hearty tone from both horns. This shows that the ground is good, as are the horns, and therefore the problem is somewhere in the positive lead from the relay to the horn.
Though I was hesitant to do permanent surgery to remove the connector, I knew this was now the most likely problem. upon removing the connector and cutting into the wire, I could see the obvious corrosion that was just under the wire insulator. After cutting another 1/4 inch, I was into clean copper again. I stripped the wire, twisted it around the blade on the horn, and suddenly, with a press to the steering wheel, my horn is back to telling kids on cell phones to quit drifting into my lane.
I hope that wasn't too long winded, and I recognize that this thread has been dead for years now, but I wanted to post just to help out anybody who was looking for the answer here like I was and didn't get quite what they needed from the previous posts.