horn resistor etc

[larry harding]

i set my ccpu up with 12 volts - ground, i know a sin in some purists eyes. everything is just better on 12v in my personal opinion, as i have converted several bikes and so on to 12 v over the years. i ordered the voltage drop from mikes in ga. the drop looked like some kind of ceramic resistor(didn't appear to be wire wound) with a heat sink. the horn sounded weak but worked, more of an aaaaah......oooooo.......ga. not the crisp sound i wanted. after a dumb mishap i accidently burned the field coils on that horn. i had another horn that blows fine, but wouldn't work at all through the resistor. i wonder if this resistor is passing enough current to blow the horn. i did electrical work all my lifew so i know i've got a circuit all the way to the horn button. if i ground the connection in the switch on the stearing column i get an arc but no noise from the horn.
next question... i'm going to try and rewind the field coils in the first horn. somewhere on this site i saw something about winding twice the turns usinf smaller wire and making the horn 12v. are there any details on this converion?

[Badpuppy]

https://www.fordbarn.com/forum/showt...sion&showall=1

24 ga. magnet wire, same direction, twice as many turns. I saw a detailed procedure once somewhere, but I can't find it now. But it ain't rocket science.

[Tom Endy]

Converting the ahooguh to operate from 12-volts is best done by re-wiring the field coils. Dropping resisters on the market do not hold up well with the power requirement.


A friend and I have done several with great success. Attached article may help. A word of caution, when you reassemble the horn make sure you line the center button up correctly with the ratchet wheel.


Best to make sure the horn works properly on 6-volts before staring the conversion. Mark how the horn is assembled and reassemble the same way.


Tom Endy

[larry harding]

thanks guys, you've confirmed my suspicions about the resistor. when i was young in the appliance repair business we would take appliance motors in to be rewound(boy! times have changed) and occasionally watched the guys rewind field coils for those motors. rewinding these coils should be an interesting challenge.

[Badpuppy]

This is from http://www.mafca.com/tqa_electrical.html -

HORN REWIRING
Question:
I would like to know how to rewire a Model A Sparton Horn from 6 volt to 12 volt. What size wire? Number of turns?

Answer:
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.

(Could have been written by Tom as well.)

[gustafson]

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better to go back to 6V, 12V not necessary