After browsing a few dozen horn issue threads I can't find a circumstance that duplicates mine to troubleshoot from:

-Truck was parked on a dry day. Only possible environmental factor was there was a bit of a temperature drop from 70's to 50's in a couple of hours.

-Truck parked engine off for a couple hours, horn starts blaring non-stop.

-After 30 seconds or so realize its my truck. Go out, get in truck, turn truck on, push (bang) on horn, horn stops.

I thought that was the end of it, today on my way into work, realize the horn isn't working.

Horn doesn't work when you press the horn, horn DOES NOT chirp when you lock the truck via keyless entry.

Haven't had a chance to try cruise control yet.

If I've read correctly, possible issues are:

horn relay
clock spring
short in horn wiring?

I haven't yet checked for a blown fuse.

If the cruise does work, does that provide a final indicator or the issue?

If a fuse is blown does that indicate anything?

Does the horn not working when I chirp the keyless entry eliminate the clock-spring as a possible problem?

 

OK, when you push the horn button, you ground out a wire, which is attached to a relay. That relay energizes, causing power to flow to your horn and the horn itself to produce loud noise. Obviously, there is also a second ground path that energizes the horn when you lock the doors with the remote. Either the relay is stuck, or the input lead is grounded somewhere it isn't supposed to be grounded.

A blown fuse will not make your horn blow continuously, HOWEVER it will make your horn stop working.

If your cruise control works, then the clock spring probably isn't the issue, but there is still a slight chance it could be the clock spring.

I would start with the horn relay.

 

cruise control works. I'm guessing it is the relay.

thinking back over the last couple days. I do recall smelling a very faint "electric burning" smell the day after my horn was stuck. smell is gone now, but perhaps that was related. (or perhaps not, that was also coincidentally the first day I had the heat on on the truck since spring. could have been dust in the heat system smelling)

If the cruise control works, its not the fuse correct?

Thanks for the suggestions!

 

The cruise control is probably protected by a separate fuse. The burning smell was probably related.

 

Took the truck into the dealership. They said the relay is integrated into the central control box. $645 to replace that.

Probably not going to have them do it. I don't need a horn that bad.

 

Dealer said I needed to replace the central junction box (he called it the central control box) but I think its the CJB and one of the horns was bad.

Wants around $900 to replace it all.

I went online and I think the Central Junction Box is only $130 (4C7Z-15604-AC) ($101 online)

Horn is only $53 ($35 online)

I don't know where they come up with $900 for the entire job.

I'm thinking of doing this myself. How hard are the horns to access?

Replacing the CJB can't be hard either? 4 screws unplug all the connectors and replug them in the new? Am I missing anything here?

 

Ok last attempt at a search for advice...

I got the truck back from the dealer.

They replaced the horn fuse and the horn works, but only the high-tone.

The dealer wants to replace the horn and the Central Junction Box.

If the horn is working fine now. Doesn't blow a fuse, but the low-tone isn't working... I'm wondering if the odds are the horn (low tone) is what shorted out and blew the fuse and the relay is fine.

Seems to me if the horn continues to work fine (high-tone only) I should just replace the horn and not spend the extra $500 on the CJB (part and labor)

Seem logical?

Second question, how hard it is to get at the horn to replace it?

 

Hi, did you ever figure out what was wrong with the low tone horn? Mine is doing the same thing, high tone works, low tone doesn't. Actually, the low tone horn works for a couple weeks then doesn't. Any ideas? Is it just the low tone horn or is there something else going on?

 

Just checking to see if anyone ever figured their horn issues? CC works but the horn fuse keep blowing and I only have the high pitched horn sound…

 

Yes, change out the horn assembly. Mine didn't work for years and then I replaced it. There was corrosion and that was the culprit.