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The horn on my '60 bugeye has always made a raucous noise, not a nice, mellow BEEP as all good horns should. Finally, yesterday, I decided to fix it. I learned a lot from the experience.
First, I took the horn off and tested it on my workbench. Believe it or not, the coil resistance is only a little over an ohm, so the sucker pulls something like 10 amps when the coil moves the diaphragm! The average current, which I measured, is about four amps, which seems like a lot just to run a modest little horn. It does explain why the horn button and slip ring, in the steering column, tend to stop conducting--and the horn doesn't work--unless all the parts are in perfect condition. It's a lot of current for some of those contact connections.
I also discovered that you can adjust the loudness and, to some degree, tone of the horn with the screwdriver adjustment in the center of the diaphragm. Screw it in too far, it sounds ugly; out too far, and it's not loud enough. I played with this until my ears were ringing and the neighbors were looking out their windows at me. But, you can get it adjusted nicely if you can tolerate some loud noise while doing it. Reinstalled, all seemed well.
So, today I was driving along, fat, dumb, and happy, and suddenly I heard BEEEEEEEEEEEEEEEP! The horn was stuck on. Fortunately, I wasn't following a carload of LA gang types, so I still have my life, always useful. I pulled over, disconnected one wire, and it didn't stop. Aha! I knew immediately what the problem was! The side of the horn circuit that goes through the horn button to ground was shorted internally! I disconnected the other side and all was quiet. Whew!
So, later today I took the horn apart. There are two large terminals inside the case, to which the wires are connected. One of these is very close to the case, and I suspect that it shorted to the housing. The fix was simple; just bend the terminals back a bit. Even so, I decided to replace the horn with one from Pep Boys (I know; sacrilege!) which draws about half the current. I'll keep the original horn, just so I can return to originality if ever I want to.
By the way--this is the horn that has a flat diaphragm and a hemispherical cover on its back, held on by one screw. I suspect this is the original horn; in any case, it's a Lucas horn, so I suspect others are similar.
First, I took the horn off and tested it on my workbench. Believe it or not, the coil resistance is only a little over an ohm, so the sucker pulls something like 10 amps when the coil moves the diaphragm! The average current, which I measured, is about four amps, which seems like a lot just to run a modest little horn. It does explain why the horn button and slip ring, in the steering column, tend to stop conducting--and the horn doesn't work--unless all the parts are in perfect condition. It's a lot of current for some of those contact connections.
I also discovered that you can adjust the loudness and, to some degree, tone of the horn with the screwdriver adjustment in the center of the diaphragm. Screw it in too far, it sounds ugly; out too far, and it's not loud enough. I played with this until my ears were ringing and the neighbors were looking out their windows at me. But, you can get it adjusted nicely if you can tolerate some loud noise while doing it. Reinstalled, all seemed well.
So, today I was driving along, fat, dumb, and happy, and suddenly I heard BEEEEEEEEEEEEEEEP! The horn was stuck on. Fortunately, I wasn't following a carload of LA gang types, so I still have my life, always useful. I pulled over, disconnected one wire, and it didn't stop. Aha! I knew immediately what the problem was! The side of the horn circuit that goes through the horn button to ground was shorted internally! I disconnected the other side and all was quiet. Whew!
So, later today I took the horn apart. There are two large terminals inside the case, to which the wires are connected. One of these is very close to the case, and I suspect that it shorted to the housing. The fix was simple; just bend the terminals back a bit. Even so, I decided to replace the horn with one from Pep Boys (I know; sacrilege!) which draws about half the current. I'll keep the original horn, just so I can return to originality if ever I want to.
By the way--this is the horn that has a flat diaphragm and a hemispherical cover on its back, held on by one screw. I suspect this is the original horn; in any case, it's a Lucas horn, so I suspect others are similar.
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