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Sparton horn not working
Posted: Mon Apr 13, 2009 8:09 pm
The Sparton Model U horn on our boat is not functioning. I took it apart and cleaned it out and checked the wiring. It has voltage all the way to the internal terminal. I have no idea how a horn makes noise. Can these been rebuilt? If so, who does it, an automotive electric shop? Any information would be greatly appreciated. See picture below.
Posted: Sun May 17, 2009 7:01 am
I'm sorry you didn't get any replies to your question. I don't know a whole lot about horns but I do know electrical circuitry so let's see if I can get you started in the right direction.
The main working part of a horn is the sound coil, exactly the same construction as a speaker coil. This coil is attached to a diaphragm (like a speaker dome)which vibrates when voltage is applied to the coil terminals and as it vibrates it produces sound waves which comes out as the beep sound we hear when the button is pressed. There is also a set of contact points inside the housing which works a little like a set of points in your distributor making and breaking to send pulses of electricity to the sound coil. There are several common possibilities when a horn doesn't work; 1. the contact points maybe either corroded so that they don't make contact or stuck together so they don't open and close, you can start by carefully seperating the contacts with a jewelers screwdriver just to make sure they're not stuck, then spray them down with contact cleaner and run a piece of paper between them (nothing more abrasive than that) 2. The sound coil may have an open circuit (broken wire in the windings). You can check the coil by removing the wires from the terminals and attaching a continuity tester across them, if there is continuity then the coil is good, if not then it's shot. 3. Bad horn button/switch, this can be tested with a volt meter checking the wire coming from the button to battery positive as most horn buttons switch the ground wire not the hot. If there's voltage when the button is pressed the switch is good, if not - well, you know. 4. There's also a horn relay somewhere in the circuit that has three wires attached to it that uses low current from the button to send high current to the horn sound coil. This gets tested the same way as the button, voltage in/voltage out when power is applied to the coil terminal.
Well, there's some basics to start with. Post more questions if you need help.
Posted: Sun May 17, 2009 7:48 am
Thanks for the reply Craig. The horn has actually been sent out to The Horn Shop in New York. This guy is old school "and that's how he likes it." No website, no cell phone, just a guy who fixes and rebuilds horns, nothing else. We hope to have it back by next weekend. His initial quote was very reasonable and he thinks it can be repaired or rebuilt.
Posted: Sun May 17, 2009 9:18 pm
Hi, could you please post some contact info for The Horn Shop?? I have one old electric horn that I have considered getting repaired. I just couldn't find anyone that worked on them.
Posted: Mon May 18, 2009 3:24 pm
The Horn Shop
I don't have his address with me, but you can reach him at the number above. He was very quick in fixing and returning our horn before a busy Memorial Day weekend. It came back in perfect working order Saturday and is back on the boat.