Mag or Battery

[Dan Hatch]

If a horn only has 1 terminal it be most likely a battery horn ?
I have two horns. One has 1 terminal the other has 2.
I know the 2 terminal horn is mag, so the other is battery?

How about 6 volt horn on 12 volts?

[George House]

Your last question: It’ll work, last a long time and be extra loud….

[DHort]

I thought one terminal, it has to be grounded. Two terminals needs no ground. I could be wrong.

[kmatt2]

From your pictures of the two horns, I would say that they are both mag horns because of the motor housing shapes. The battery horn would have a longer motor housing. The two wire horn was for a wood firewall car and the one wire horn was for a metal firewall car that was sold new as a non-starter car because the metalfire wall to T frame made the ground connection.

[Dan Hatch]

Thanks for info. I may just change my 16 to a later battery hour. Mag will only work with engine running. Dan

[Steve Jelf]

If there's an adjusting screw in the center of the diaphragm it's a mag horn.

[TRDxB2]

From https://www.mtfca.com/discus/messages/80257/93504.html
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By John F. Regan on Thursday, May 28, 2009 - 11:46 pm:
Guys - let me shine some light here if I can. Starting in 1915 with that version of the mag horn and continuing up until but not including the "combo" light/horn button, the wiring was as mentioned namely that the wiring was from magneto to one horn connection and then from other horn connection to the button and there grounded at the column. Either horn connection could be used for either wire since the source is AC but both of the horn connections must be isolated from ground. Only 1 wire comes to the horn button up the wiring tube. The earliest 1915 cars had a loop of wire and the button was in fact clamped to one of the steering wheel spokes. Bet that made things interesting on sharp turns and horn honking. Starting with the "combo" light switch, the magneto wire was brought all the way up to the switch where it was connected via horn button to the horn wire which then ran back down to one horn connection. The other horn connection went to ground simply by having the fiber washer removed at that remaining mag horn connection which then grounded it since the horn frame was connected by one bolt to the steering column base. The reason why the mag wire was taken up the column was that the combo switch could at that point connect that same magneto wire to either of 2 connections (brite or dim) which came back down the column to be connected to the dimmer coil which on these first 1917 cars was mounted to the engine side of the dash. The dimmer coil was used with the "combo" switch to start and then later moved to a spot behind the ammeter block off panel on the later T's.

To sum it up - cars with simple button on column (typically 15/16/early 17?) use fully isolated connections on both mag horn terminals while cars with combo button/switch and later cars use the mag horn with one connection going to ground and the mag wire being supplied to the horn button with the horn hot wire coming from the other side of the horn button such that neither side of the horn button is grounded in these later cars.
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By Jim on Friday, May 29, 2009 - 12:38 am:
John Regan--- I notice some magneto horns only have one terminal. When were they used?
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By Warren Mortensen on Friday, May 29, 2009 - 08:01 am:
Those were used on later non-electric (no generator furnished) cars. The horn button had two wires (one going up and the other going down to the horn). One wire of the horn armature was connected to the horn case internally. Since the horn was bolted to ground (engine block or steel firewall?) it needed only the hot terminal.
Regarding the later electric horns that operated on the DC circuit rather than magneto: I believe Ford didn't start furnishing cars with this horn until well after the gen/battery option was offered. Early cars with generator option still utilized a mag horn until sometime in 1922 if I recall correctly. Regan may be able to give better details.
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By William C Severn on Friday, May 29, 2009 - 11:16 pm:
Thanks for the great input from everyone. I should be able to get the horn working in short order.
Bill
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By John F. Regan on Saturday, May 30, 2009 - 08:59 am:
Warren is correct. Battery horn was supplied first in early 1922 and believe it or not that first battery horn was mounted to the firewall with a rare bracket known as 6237B which was similar to the pre 1922 mag horn bracket (6437A) in that it was "butterfly" shaped but it had a "z" shaped bend in the middle of it to mount it forward of the firewall since it had a large and deeper motor cover than the mag horn. This bracket was only used a matter of a few weeks before the horn was fitted with a new bracket (6437C) and mounted to the motor via one head bolt and one water inlet bolt. The final bracket was 6437D and was the typical 26-27 bracket which mounted the horn via the water inlet bolts only.
What may not be obvious is that the magneto horn casing was always grounded even on the early cars wthh wood firewall because one bolt of the mag horn mounting was one of the steering column mounting bolts at the steering column firewall flange. Thus when the mag horn began to be powered by a single wire mag lead coming from a pushbutton, the horn was grounded either by that steering column bolt on the early cars or by an engine bolt on later ones. Warren nailed it on the single connection mag horns. Those were later. Earliest mag horns came in all sorts of varieties and shapes but generally were characterized by having rather short snouts (called the horn bel) and some of those were painted brass. Later mag horns had the longer snout like the battery horns and were steel.
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By John F. Regan on Sunday, May 31, 2009 - 06:25 pm:
OOPs! The early battery horn bracket with the offset Z bend in it is 6437B. I incorrectly called it 6237B.

[Dan Hatch]

Thanks. Think I’ll dig out a battery horn and save the mag horns.

[signsup]

For what it's worth from a newbie, in my other hobby, lots of experience with 6v and 12v mix and match. I have a 6v two wire horn on the ambulance right now on a 12v battery and it is loud but has a metallic buzz to it with no adjustment screw to deal with that, so like the ring gear, I feel like I'm putting a strain on it every time I use it.
If I were keeping the 12v set up on the ambulance, I'd look into a resistor and wire it into the horn circuit. And, if I hav 6v light bulbs, I'd wire them into the same resistor.
But I'm leaning towards runnning the T on 12v the head lights on 12v and adding a 6v battery into the mix and starting the T and running the horn and siren on the original 6v. I have room in side mounted tool boxes for two batteries and the needed distribution blocks. I feel the T runs better on 12v, I have no working mag but don't like the harsh start up on the 12v. The two batteries with some sort of switching wiring set up will give me plenty of power options.