My 2001 Tahoe horn just started honking today while I was at work. It wasn't the car alarm in a series of 'beep beep beep'. It was contantly honking. By the time I was alerted to it and was able to figure out which fuse I needed to pull to make it stop, it quit honking. Apparently the fuse had blown, and this made it stop. When I pulled a similar fuse from another spot and put it in, it started honking again. With the good fuse in place, I pulled the relay and swapped it with another one of the same type. This made it honk as well. So the relay seems to be fine and I will need a new fuse. But it will continue to honk. My guess is that something in the steering wheel failed and put it in an ON position sending a signal to the horn. I figure that if something broke past the fuse/relay in the circuitry, then the horn would blow regardless of the fuse or relay. But since the blown fuse made it stop, I figure whatever signal was going to the horn was cut and so the horn quit honking. Any suggestions?

 

have you added any accessories that might be causing a short?
Can you push down on the horn button and feel it engage dis-engage?
Do you use your horn a lot?
I would suspect the horn button in the steering wheel.
disconnect the horn and put a volt meter in place (or light bulb) so you can troubleshoot
without the horn going off.
And definitely don't ride behind any biker gangs until you know its fixed

 

Be careful of the airbag.

 

No, no new accessories.
No, I do not use my horn very much at all.
Last evening, I pressed on the horn several times and also pulled it back towards the seat to see if it was stuck in the ON position. I guess I made it release b/c I put in a new fuse and it had stopped honking - where earlier in the day a new fuse would have allowed it to keep honking. I pushed on the horn a few times and it worked. Tried setting off the car alarm and it worked. I can't figure out why it just decided to go off. The temperature was probably in the low 70s when it went off yesterday, and I'm sure it was a little warmer than that in the car. Don't know if that somehow affected the button in the steering wheel. I don't know if it is fixed or not. Guess time will tell.
When you say "disconnect the horn and put a volt meter in place", I assume you mean disconnect the wires leading into the actual horn itself and place the volt meter there inside the connector? Sorry, but I'm a bit mechanically challenged.
I'll try to avoid those gangs for a while.

 

Yes disconnect at the horn itself, and as Shark stated be careful of the air bag if you choose to tackle this yourself.
If you were able to pull back on the steering wheel padding that makes the horn go off...its probably the horn button inside that is the problem.

Has anything been spilled on it?
Maybe a piece of debris or a coin has gotten in there, or maybe its just a bad button/contact.
Either way I think you have found your culprit in the horn button area of the steering wheel.

 

I had a similar problem on dad's old CJ7 where the contacts in the horn switch built up scorch from arcking open and closed. Occasionally when you blew the horn it would stick and you'd have to beat it to stop it from honking. This was caused by a lack of detent ("snap action") which is in turn caused by a lack of spring tension in the horn switch.
I'm not sure if the horn switch is at all similar to one in a '79 Jeep, but thats the only cause that I can think of that fits the symptoms.