12 Volt Conversion with 6 Volt Horn

barkleydave:
I just removed the armature and carefully counted the turns as I unwound the field coils and then carefully rewound them in place. There aren't that many turns. Just remember to wind twice as many turns with the finer wire as you removed. The spool of wire I listed will do all of yours and probably everyone else you know with a 12 volt system.
 
I was able to find smaller quantities of 23 or 24 gauge magnetic wire on ebay. Here's a post I saved from somewhere:

To change the Model A horn from 6 volts to 12 volts, you must rewind the two field coils. Leave the armature as it is. First disassemble the horn to remove the brushes and the armature. Unsolder the two wires at the connector clip ( one from each field coil.) Note the direction of winding on the coils. The two coils are wound in opposite directions. The rule of thumb is that when you double the voltage, you use 1/2 the wire size and double the turns. So going from 6v to 12v use 24 gauge wire (original wire is 20 gauge, 1/2 that size is 23 gauge, but almost impossible to find 23 gauge so I have always used 24 gauge readily available at Radio Shack). Six volt coils have 45 turns and I have been using 100 turns with 24 gauge wire with great success. Be sure to use coated wire, normally used to wind RF radio coils or speaker coils. After winding the horn coils I usually brush a coat of light varnish to help insulate. The windings do not need to be real tight or in neat rows. In fact I found that if I wrapped just tight enough to form the wire around the core, and laid about 6 or 7 turns per layer, without being too careful how straight each wind was, I got better results on horn operation. In looking at a lot of original horns, some were manufactured with very precise and straight windings and some were wound very haphazardly
 
I think I have reached the end of the line on this horn!
I decided to remove the horn and clean it and dress the brushes and lube.
In preparation for rewinding for 12 V.

My problem is it would work a couple of times (terrible sound) then not work at all. I tried every possible adjustment and it would still have dead spots and not spin.

After I cleaned it up I hooked it up to a 6 volt source and it sounded pretty good on the bench. I then decided to try the resistor and 12 V. Horn barely turned and the resistor got super HOT in less than 2 seconds. Second attempt nothing!

For some reason this horn motor is drawing a lot more amps than it should! It is a reproduction horn which looks great but now on the shelf.

I ordered a new horn to complete my project (ouch!) ...and will play around with the horn and try rebuilding it as a spare. It still works on 6 volts so might just sell it and be done with it.

Thanks for all the help and ideas
 
The original 6 volt horn takes about 5 amps to blow, when the adjustment screw is set correctly. If you then use a 12 volt battery you need to drop 6 volts, so 6 volts X 5 amps = 30 watts, which is a lot of heat. I would buy a 1 to 1 1/2 ohm resistor rated at 50 watts, so it won't overheat. If you do a lot of horn blowing the resistor will heat up, and the more it heats the more resistance it offers. Check ebay and you can buy a nice finned aluminum 1 ohm resistor rated 50 watts for a few dollars with free shipping. Like most things these days, it comes from China and takes about 2 to 3 weeks for delivery.
 
I read all the comments in this thread. I have the same setup but the horn does not sound ,I only hear the horn motor turning . Try all adjustments and still no sound . Check my wires and the yellow is the the altnator and the blue /yellow is to Horn button . I even took the Horn off and wire tested from battery and ground with no changed

Any one run into this problem?

Skip
 
You need to adjust until the armature turns with a little drag. Then it should sound OK. Too much drag and the horn won't sound or turn. Too little drag and the horn will turn but not sound. Just got finished selling 15 horns. Only one needed new windings. Best sounding and loudest horn is one with the new A&L reproduction motor which costs about what rewinding does @$100 or so and looks identical to an original with the cover on.
 
I've used both resisters mentioned and they both work well. Like someone said you can use the 6 volt horn on a 12 volt system as long as you don't run it for extended periods. A simple Ahooga occasionally is no problem. Someone suggested rewinding the horn motor that would also work. The other option is getting a horn motor from A&L which is new and available in either voltage.
 
MRTEX

thanks for the info will try that , Did not want to buy a new horn ,the one i have was new 5 years ago and I just finished the conversion over to 12v.


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dustyp489 said:
I read all the comments in this thread. I have the same setup but the horn does not sound ,I only hear the horn motor turning . Try all adjustments and still no sound . Check my wires and the yellow is the the altnator and the blue /yellow is to Horn button . I even took the Horn off and wire tested from battery and ground with no changed

Any one run into this problem?

Skip
Click to expand...

Something broke in the horn. The ratchet is not turning. Could be the nut on the armature came off or the armature broke.
 
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