I am installing a new Fiamm horn (electric, not airhorn)

The new horn only requires a 10 Amp fuse so I am using the existing horn circuit. I removed the old horn, spliced a connector on it for the hot line, ran a ground wire from the ground bolt in the front, left engine bay(by the intake).

Here is the problem. When the horn is not mounted on the car and just lying on the floor or in my hand it works fine. When I mount it on the car on a small bracket in the existing location the horn works fine until I tighten the bolt fully. When the bolt is loose it still works fine. When I snug it up that finally turn the horn starts sounding like it is playing under water. Muffled and fuzzy and not very loud. I tried isolating the bracket with rubber washers around the bolt and that doesn't seem to make any difference.

Any tips from you horn/electronics gurus here?

 

How is the bracket attached to the horn?

 

Just like this install by tedser but only 1 horn and the extension bracket is not used. Only the small L bracket form the frame to the horn itself.

 

I am submitting my opinion with absolutely no experience on this subject...

Now that I've said that, I think the problem may be caused by overtightening, not a ground problem. Maybe the speaker for the horn is attached to the assembly at or near the same point that the bolt is attached to. Now, as you tighten the bolt, the speaker is being pulled backward. The other side of the speaker is probably attached to the black plastic horn part, and the tightening of the bolt is pulling the speaker tight. This could cause the "underwater" effect.

...But I could very easily be wrong.

 

[QUOTE]Originally posted by djqube
[B]I am submitting my opinion with absolutely no experience on this subject...

Now that I've said that, I think the problem may be caused by overtightening, not a ground problem.

 

[QUOTE]Originally posted by TrojanHorse
[B][QUOTE]Originally posted by djqube
[b]I am submitting my opinion with absolutely no experience on this subject...

Now that I've said that, I think the problem may be caused by overtightening, not a ground problem.

 

Lock or star washers

 

Or one of those Nylock (Nylon inside) nuts?

 

Is the bolt to long? Maybe it is making contact when tightened all of the way. Try adding a couple of washers.

 

Thanks to all. Turns out it was a ground fault problem. The ground path is much shorter through the bracket than through the line up to the ground bolt. I swapped the bracket around a bit so that it didn't touch the painted portion and it fixed the problem. When I touched the painted part the fuzzy, underwater sound happened. Lesson learned is to sand the area under the bracket to get a better ground.

Now that I am all done I am not too impressed with the new horn. I may go for the Hella Supertones after all.