My neighbor had the same problem on a 05 ultra, we put a airhorn on and it also only worked half the time. He took it to the dealer and they replaced the alternator, it works fine now.

 

About 3 months after i bought my 06 road king my horn would only work about 30% of the time. I had the dealer "fix" it since it was under warranty. 1st time they put a new horn on - it worked for about 3 weeks and 2nd time they exchanged some wiring and its worked fine ever since

 

Get it done under warranty. If, and when, you decide to swap out horns, you will have a working product to sell on ebay, or somewhere else. Just my $0.02.

 

Lots of good ideas. Let me say that when the horn doesn't blow, it kinda makes a "humming" (maybe that's the wrong word) noise, but it does try, I mean it's not dead. Would that still be a wiring problem?

Anyway, I'm gonna run up to the dealer tomorrow and let them fool with it.

Hack

 

I was told when I took mine in for a "croaking" now and then that they changed companies and have changed back. I still want to get a mini beast though.

 

My horn has done this twice. I thought it was just dumb luck. Now I know there are others....

 

The chrome horn cover and metal bolt cause some kind of electrical problem that makes the horns fail. It really is amazing that HD sends them out that way.Take off your horn cover and you will see it works fine. I have a fiberglass skull horn cover and now mine works fine.You can put some black tape around the part where the horn cover bolts to the horn and it should work.

 

Get you some BJ's air horns. I like mine!

 

Had the same problem with my 07 ultra horn. Was told by one of the servise people to give it a good soaking with WD 40. Have not had a problem with it since the soaking.

 

Watch for Finger!!!