I have a Explorer Sport Trac, that has a constant, horn blowing. Nothing I can do to make it stop except remove the fuse or horn relay.

I have disconnected the clock spring wires, from under the dash, to make sure it isn't anything horn contacts or clock spring related.
The horn relay has constant power on the control side (12v), when the fuse is installed, which means the load side is connected. This makes me think there is a ground issue somewhere, that is completing the circuit. But I can't find anywhere it is grounded or a bare wire.

If I connect a probe light on the + side of the battery terminal and touch the yellow/green wire under the dash (horn wire), I get an illuminated light. I think this indicates a grounding issue somewhere, since that wire should not be grounded, except when connected to the clock spring and the horn is depressed.

I have looked under the dash and under the hood, under the fuse box, and everywhere I can think of to look for a bare or rubbing wire, but no success.
Here is how the problem started:

Bought the rig for my son. The rig had broken cruise control switches, so we replaced them. Had to disconnect battery, remove the air bag, remove the existing switches by unplugging them into the clock spring, and then putting stuff back together. No big deal. Didn't turn the wheel, or yank any wire, or jack with anything else. When I connected the battery, the horn started honking (on/off/on/off and so on). Then it went from on/off to constantly on. I figured it had something to do with the aftermarket alarm, so I had a shop rip out the aftermarket alarm. No luck. I put the fuse and relay back in and the horn still blows constantly. My neighbors are a little tired of me troubleshooting it, and I have literally taken the rig apart in my driveway to inspect the wiring in the dash, pulled the radio, under the hood, taken the wheel liners out to check the wire. I can find anything.

The ONLY think I can think of, is that the security module must be fried or something, because I know that controls the honk-honk when you lock or unlock the doors. Never heard of this being an issue, or can find anyone else having this problem, but either I fix it or the dealership has to dig into it for a lot of $$$$$.

 

When you used your test light on the horn wire under the dash, was that with all connections still connected or with the clockspring disconnected? If still connected, try again with something unplugged, then determine which side of the connection is shorted to ground and which side is floating. That will give you some direction on which side to start looking to for an issue.

Since all this started though when you changed the steering wheel buttons for the cruise control, it seems like there's a high probability something you disturbed during that process is the cause, and that's where I'd suggest disconnecting and starting your test light measurements from.

Good luck on the troubleshooting. You could always pick up another test light or make your own with some wire and a 194 bulb or something to substitute for the horn. That way you and your neighbors don't need to listen to the horn during troubleshooting but rather look for the light.

-Rod

 

Ever find the problem? I have the same thing happen to me. 2002 sport trac. Replacing the cruise control buttons and didn't unplug any thing but that.

 

Almost all US made horns use the same system of constant power +12 and pressing the horn grounds the circuit out, making it honk. That's why you can blow the horn, even when the vehicle isn't running.

If your horn is constantly blowing, the horn switch assembly is grounding out somehow.

 

If the horn stops sounding when you pull the relay, there is a short to ground on the control side..

 

So did the horn issue happen as a result of replacing the cruise control buttons, or you replaced the cruise control buttons to try to fix the horn issue?

If the horn issue happened after replacing the buttons, I'd suspect that you probably adjust the tilt of the steering column in the process which may have stressed the wiring harness and possible pulled the horn wire out of the connector which is now laying against a ground. There have been other known issues with the wiring harness in the steering column being seemingly too short for the tilt range of motion. The horn signal also goes through that cruise control switch assembly, so it's possible the switch assembly is bad/malfunctioning and grounding the horn circuit.

I'd suggest you disconnect the harness at the "sliding contact" (aka clockspring) and check each side of the connector for the yellow/green wire in terminal location 2 for continuity to ground. That will let you know if you need to disassemble the cruise control switch or check the harness between the clockspring and horn relay.

-Rod

 

I did find the problem with my. I plug the wire in backwards on the clockspring from the cruise control.