Old Antique Horn Fix

What can I do to free these old horns up? I think they’re just rusted because one time they ALMOST worked. A friend said to spray some lube in them and turn them upside down for a while. (1950 cadillac)

Trying to get a picture. Attach link not working


With cover on

Maybe use some spray electrical contacts/tuner cleaner?

Yeah I’ve got a little leftover radio shack electronics cleaner, some liquid wrench, and some b12 chemtool carb cleaner. I wonder what concoction will work!!?

If there are some contacts, I’d sand them.

Well, no luck. Electronic cleaner sprayed the electronic stuff and carb sprayed into the horns, scratched the wire contacts with a flathead screwdriver and buttoned everything back up and nothing. I’ll figure it out sometime

Contact cleaner and sometimes I’ve had some luck just by tapping the whole thing against something hard while completing the circuit.

I’ll have to try that. Somebody rewired them outside of the old harness and put an aftermarket button under the dash. So my buddy tapped on them while I was holding the button and we had for a second the most faint little sound, but then nothing. So I think its hiding in there somewhere, just gotta mess with it more.

Try adjusting the lock nut gizmo I see.

Just get a bulb horn. These bulb horns are reliable and all you have to do is squeeze the bulb when you want the horn to honk. The original Cadillacs back in the 1900s had bulb horns–why would you want anything more?

However, if you really think you need an electric horn, you might be able to keep spraying the contacts with contact cleaner. You may also want to use an ohm meter to check for continuity in the coils.

Well I’d like to keep the original horns working… It is a 1950 not earlier 1900’s and If someones in the way and doesn’t see me coming I need them to know! 5 tons of unstoppable steel coming their way haha.

There’s a solenoid attached to a diaphram. Energized, it retracts and pulls the diaphram inward. That action opens the contacts and interrupts the flow of current. The diaphram retracts and the contacts close again. That process repeats as long a the solenoid has power. The diaphram makes the noise. The nut adjusts the contact tension and is used to achieve the highest volume by matching the resonant frequency of the entire moving assembly.

If it barely squeaks, the plunger for the diaphram is probably rusted up. You may need to remove the “horn” by grinding off the rivets. Then you can get at the diaphram side. Just use screws and acorn nuts to put it back together instead of the rivets.

And just as I was about to ask how a horn actually works . . .

It is a possibility the horn circuit is completed by the metal clamp that holds it to the body. Make sure it has a good ground.

It appears that the diaphragm has substantial corrosion. Try cleaning all electrical contacts in the assembly and see what happens, but I suspect you’re going to have to bore the rivets out and replace the diaphragm. The diaphragm will be a stamped piece of metal likely with concentric convolutions (like the ripples around a stone thrown in the pond) to allow it to move readily in the axial plane (wobble in & out in response to the solenoid operation).

If you really want to keep it as original as possible, and I respect that, try to find an aftermarket horn of the same size or larger, bore the rivets out on the drill press, open the “can” and remove the diaphragm. Do the same to the old horn, and try to use the old diaphragm as a template to craft a replacement out of the new horn diaphragm.

Now, it’s also possible that he insulation has failed on the solenoid coil windings, but you’ll be able to assess that when you do the disassembly on the old unit. You probably won’t have access to the equipment to do a “dielectric breakdown test” (testing the insulation for breakdown under load), but you should be able to do simple resistance checks and visual examination sufficient to determine the condition of the coil.

This sounds like a huge amount of work, but it isn’t. It’s also low-risk. Aftermarket horns of this design are cheap, so if the project fails the cost is minimal. If it works, you’ll be able to hold your head proudly and brag that you’ve saved the original horn.

That’s what I’d do. Of course, you must realize my sanity has been challenged before. I would actually consider this project to be a challenge.

If you replace the solenoid with one from an aftermarket horn, your Cadillac has a 6 volt system unless someone converted it to 12 volts. If you substitute electrical parts from an aftermarket horn, make certain it is the correct voltage.

Thanks for the input guys. Yes it is a 6 volt. I’d like to hit it with some PB blaster and let it soak over night just to see if anything frees up. I’ll keep you posted.