The Ford Barn

freak · 03-26-2021, 06:03 PM

My horn sort of works but sounded like it was running on a dying battery. I took it apart today because I replacing the radiator and here's what I found inside. Can someone tell me what happened and what a fix might be? My car was converted to 12V so this may be a resistor that someone added but I don't have experience with the horn so any tips are appreciated!

Slowmotoring · 03-26-2021, 06:48 PM

Should be able to adjust the sound of the horn with one of the screws on the backside of the horn. Im not to sure about the picture. Looks like a resistor that has gotten pretty hot. Not sure if thats what should be in there or not.

rotorwrench · 03-26-2021, 07:04 PM

A voltage dropping resistor is the only way to keep a 6-volt design from sounding like a banshee for a high current draw component like a series wound horn motor. Perhaps the resistor has a bit too much resistance. Resistors make heat so that heat has to be disipated rapidly to keep the resistance within parameters. I would try a resistor that is made to drop voltage for such devices.

This link illustrates a dropping resistor mounted to a heat sink. other sources sell this type as well.
https://www.modelaparts.com/a13803

McMimmcs · 03-26-2021, 07:06 PM

Quote:

Originally Posted by freak

My horn sort of works but sounded like it was running on a dying battery. I took it apart today because I replacing the radiator and here's what I found inside. Can someone tell me what happened and what a fix might be? My car was converted to 12V so this may be a resistor that someone added but I don't have experience with the horn so any tips are appreciated!

Whoever did it, don’t invite them back to do more repairs!

JayJay · 03-26-2021, 07:06 PM

I once found a brush spring had been overcompressed and the brush was barely making contact, that gave it a very weak ahooga, more like a oaah. Tightening the adjuster screw just bound it up. Took it apart, stretched the spring back (as I waited for replacement) and it worked just fine.

Looking at that resistor, I think it would either work or it wouldn't. But that does look hot.

JayJay

Badpuppy · 03-27-2021, 09:26 AM

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The power rating of the resistor used is too low. It has burned and resistance has increased. Remove that one and buy a dropping resistor from one of the vendors and install it per instructions.

Tom Endy · 03-27-2021, 12:50 PM

The dropping resister in your horn has burned out. Most on the market cannot handle the power requirement. They work fine as long as you don't blow the horn.

The best solution is to replace the two field windings for 12-volts. It is not a difficult job, just tedious.

Attached article describes how to do it.

Tom Endy

Herb Concord Ca · 03-27-2021, 06:45 PM

If you have a 12 volt car follow Tom's advice above. His statement on horn resistors is also correct. My car is 12volts for the A/C! I rewound the field coils and the horn works great.

freak · 03-27-2021, 07:12 PM

Thanks Tom! That burned resistor in the document looks just like my burned resistor lol!

03-26-2021, 06:48 PM	#2
Slowmotoring Member Join Date: Nov 2020 Location: Upstate NY Posts: 94	Re: What happened to my horn? Should be able to adjust the sound of the horn with one of the screws on the backside of the horn. Im not to sure about the picture. Looks like a resistor that has gotten pretty hot. Not sure if thats what should be in there or not. __________________ Good things take time

03-26-2021, 07:04 PM	#3
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,422	Re: What happened to my horn? A voltage dropping resistor is the only way to keep a 6-volt design from sounding like a banshee for a high current draw component like a series wound horn motor. Perhaps the resistor has a bit too much resistance. Resistors make heat so that heat has to be disipated rapidly to keep the resistance within parameters. I would try a resistor that is made to drop voltage for such devices. This link illustrates a dropping resistor mounted to a heat sink. other sources sell this type as well. https://www.modelaparts.com/a13803

03-26-2021, 07:06 PM	#5
JayJay Senior Member Join Date: Jan 2020 Location: SF Bay Area Posts: 1,069	Re: What happened to my horn? I once found a brush spring had been overcompressed and the brush was barely making contact, that gave it a very weak ahooga, more like a oaah. Tightening the adjuster screw just bound it up. Took it apart, stretched the spring back (as I waited for replacement) and it worked just fine. Looking at that resistor, I think it would either work or it wouldn't. But that does look hot. JayJay __________________ JayJay San Francisco Bay Area ------------------------ 1930 Murray Town Sedan 1931 Briggs S/W Town Sedan

03-27-2021, 09:26 AM	#6
Badpuppy Senior Member Join Date: Dec 2017 Location: Guthrie, OK Posts: 1,144	Re: What happened to my horn? Sponsored Links (Register now to hide all advertisements) The power rating of the resistor used is too low. It has burned and resistance has increased. Remove that one and buy a dropping resistor from one of the vendors and install it per instructions.

03-27-2021, 06:45 PM	#8
Herb Concord Ca Senior Member Join Date: May 2010 Location: Concord CA Posts: 635	Re: What happened to my horn? If you have a 12 volt car follow Tom's advice above. His statement on horn resistors is also correct. My car is 12volts for the A/C! I rewound the field coils and the horn works great.

03-27-2021, 07:12 PM	#9
freak Senior Member Join Date: Sep 2013 Location: Pemberville, Ohio Posts: 456	Re: What happened to my horn? Thanks Tom! That burned resistor in the document looks just like my burned resistor lol!