Where is the ground wire placed for mag horns?

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Model T Ford Forum: Forum 2013: Where is the ground wire placed for mag horns?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas Kuhn on Monday, October 14, 2013 - 08:01 pm:

Hi all,my question is where did the factory place the ground wire for the magneto horns?I find no reference anywhere for it.I have a 1920 Roadster with 5 terminal block and wood firewall.Have everything hooked up and where it is supposed to be but don't know the location to run the ground wire from the horn terminal to where??Help!Thanks!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Monday, October 14, 2013 - 08:11 pm:

The 'Ground' wire goes to the horn button. Not sure about later models with electrics. Did they have mag horns? On our '18, there is a wire running from the mag terminal on the coil box to one terminal on the horn. Then there is a wire running from the other horn terminal, up the steering column to the horn button. When the button is pushed, it completes the circuit to ground and the horn blows.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Monday, October 14, 2013 - 08:15 pm:

I think one lead went to the coil box Mag terminal and the other lead goes to the horn button. The horn button is the ground. When pressed, the horn is grounded and sounds.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky, Lytle TX on Monday, October 14, 2013 - 08:16 pm:

Oh well, Hal has faster fingers. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Willie K Cordes on Monday, October 14, 2013 - 08:17 pm:

That sounds correct for a mag horn.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR on Monday, October 14, 2013 - 10:15 pm:

"Not sure about later models with electrics. Did they have mag horns? "

Nope, they had battery-powered horns.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jack Daron - Brownsburg IN on Monday, October 14, 2013 - 10:43 pm:

If you have a wood firewall,an extra ground from steering column to frame will help the weak horn.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John F. Regan on Tuesday, October 15, 2013 - 12:26 am:

OK here goes. Starting with 1915 the single horn button on the column grounded a single wire to that column to honk the horn. That single wire ran to one of 2 connections at the mag horn. The "other" connection on the mag horn went to the magneto post on the firewall mounted coil box. This 2 terminal mag horn was used for all cars that had the single horn wire running up to the single button on the column.

The horn wiring setup changed when the "combo" horn button/lightswitch was installed on the column which replaced the single horn button. Now the magneto wire ran up the column to the horn button and light switch. There was then another horn wire running back down to the mag horn and the remaining connection on the mag horn if it had one was grounded. That same magneto wire at the combo switch was connected to the light switch and 2 more wires came down the column (now a total of 4 wires). Those 2 wires from the light switch were the "bright" and "dim" connections to the dimmer coil mounted on the firewall. The single wire then from that dimmer coil ran to the headlights.

The early magneto horns had 2 connections and were used during the time up to and including the time of the earliest of the combo switches. Neither of those 2 connections on these mag horns were originally grounded to the horn. When they changed from the single button horn to the combo switch the factory simply used up all of those 2 connection horns by installing a ground on one of the 2 connections. They did that in TRUE MODEL T fashion but doing it the cheapest possible way. You remove the nut, metal washer (if equipped), and fiber insulating washer and re-install the same parts except you LEAVE OUT THE FIBER washer so that connection then grounds to the horn housing and since one of its brackets is fastened to a steering column bolt, you now have it grounded. It works. Some time later they no longer used 2 magneto horn electrical connections and simply grounded one wire internally in the housing of the horn. Grounding the horn to the steering column works fine for all years that did it since the mag horn was firmly connected to the steering column or its ground wire was firmly grounded there when the single button was used. In both cases they used the steering column to ground to. The magneto horn was available until the end of production and it moved to the motor when the battery horn also moved there in Early 1922. For you trivia fans - the very first of the battery horns came out in 1922 and were mounted to the firewall and not the engine. They used a somewhat rare bracket for that purpose. I have seen 2 of them.


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