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Horn button spring inside steering wheel is melting plastic case. Horn only works with heavy ground wire touched to steering column bearing. Using an add on universal button now mounted to side of dash. Any help appreciated. Thanks

Bob S,

Welcome to the Stovebolt.

Your profile doesn't indicate what year rig you are working on, but the book shows the plastic encased spring is used from '47-'57. If that spring tries to carry too much current, it will heat up just like the coils in a toaster. Is there a horn relay that has been bypassed or rewired incorrectly by someone. The circuit up the column for the horn button shouldn't carry much current at all...just what the tiny coil in a horn relay requires to close.

Stuart

Stuart. Thanks for the reply. The truck is a 1950 Chevy 3100. There is no horn relay in the system. I have a 1950 shop manual and it doesnt show a relay. Should I install one? Thanks. Bob

Bob,

That seemed to be a transition period for horn relays in the AD trucks. They were located near the driver side hood hinge on the fire wall. A horn relay would make the system better, but one has to wonder why yours is pulling so much current that it is melting things.

Before I retro fitted with the relay, I would test what is there now, and try to find why it is doing this. Could the horn have stuck at some point, and this melting thing was a one shot deal!

Your system must supply ground to a insulated horn. Maybe something inside the horn proper is gunny-bagged..I don't know. Grab your little voltage tester and do some more detective work. Keep us posted!

Stuart

Stuart. Thanks again. I'll keep you posted. Bob

The 6 volt horn on my 1950 3100 has 2 terminals on it. When battery power is connected to one terminal the other terminal has power coming out. Is this normal? Thanks.

Yes it is normal - IF you are just measuring it with a volt meter. A volt meter is high resistance so no current flows. Without grounding that second terminal you would see battery voltage. It's like measuring water pressure with the valve closed.

(from Virginia.edu/wikipedia) While some modern car horns are actually specialized computer audio systems, the old-fashioned electromagnetic car horns are still common. An electromagnetic horn uses an electromagnet to attract a steel diaphragm and turns that electromagnet on and off rhythmically so that the diaphragm vibrates. In fact, it uses the diaphragm's position to control the power to the electromagnet. Whenever the diaphragm is in its resting position or even farther from the electromagnet, a switch closes to deliver electric current to the electromagnet. The electromagnet then attracts the diaphragm's center. But when the diaphragm moves closer to the electromagnet, as the result of this attraction, the switch opens and current stops flowing to the electromagnet. Because of this arrangement, the diaphragm moves in and out and turns the electromagnet off and on as it does. The diaphragm's tone is determined by the natural resonances of its surface.

As soon as you ground that 2nd terminal the voltage would fluctuate up and down at the frequency of the vibrating horn. If there is something wrong in the horn to keep it in the resting position (ie rusted) it would be a dead short and cause the horn button spring to get too hot.

Paul

Bob S,

Yes. To make the horn sound, that terminal must find ground...that completes the circuit.

Stuart

Thanks all for your help. I finally took the new steering wheel contact and spring button apart that I ordered from Jim Carter Truck. From research on the internet I found most contacts have a heavier wire going thru the center of the spring. The new one from Jim Carter had no heavier wire at all, just the small spring which fried everytime I hit the horn. So I soldered a wire thru the spring between the contact on the steering collar and the contact on the horn button end. Horn works fine now. Thanks again. Bob S.