Horns - 6 to 12 volt

[Drbrown]

My 6v horn relay was not working and prior owner changed system to 12v. Put in a '56 Ford 12v relay and have changed the 6v horns to work in-series to accommodate the 12v change. Each horn is mounted on a vertical metal strut that comes up thru the belly pan in front of the radiator. Those struts provide each horn with separate electrical ground connections.

Horns were made by Sparton and castings are imprinted "LO" (right side) and "HI" (left side). Main body is die-cast metal and dome covers stamped-steel. The die-cast body did not rust and mild surface rust on and inside the domes cleaned-up nicely.

Substituted the metal strut under the left horn with a matching home-made polyester piece (88 cents at Walley), eliminating its elec ground connection. Then connecting that horn to the right hand horn lets them operate in series. Although the voltage thru the circuit is dropped, I notice that the loudness of the right hand horn seems comparatively less .... no big thing .... one can switch the "HI" and "LO" pitched horns if desired.

Oddly, the horn trumpet opening faces upward. I thought that was an invitation to water damage but any water that leaked in was able to drain out an opening in the bottom of the assembly leaving limited damage. The manufacturer provided a durable design and brass nuts on all parts. (here come the playful comments)

[koates]

Horns cant work connected in series, have to be in parallel. Either run them on 12 volts for a louder and rough out of tune sound or with a resistor in series with each horn to drop the supply voltage to 6 volts for the correct in tune sound. Regards, Kevin.

[Charlie Stephens]

Originally Posted by koates

Horns cant work connected in series, have to be in parallel. Either run them on 12 volts for a louder and rough out of tune sound or with a resistor in series with each horn to drop the supply voltage to 6 volts for the correct in tune sound. Regards, Kevin.

I may be wrong here but I assumed you could run two 6 volt horns in series with a 12 volt system. Each horn would see 6 volts across it assuming that they both had the same resistance. What am I missing? Of course the first horn would need to be isolated from ground so the current would flow through it to the second horn (and not to ground as normally encountered).

Charlie Stephens

[ford38v8]

Kevin, Drbrown wasn't asking if it would work, he was telling how he made it work.

Kinda looks like the key to invention is to not have advance knowledge that it won't work.

[Fordestes]

I connected two 6volt horns to 12 volts in series by mounting on a wood insulator, had one a little louder so I switched positions and was so loud every neighbor on the block looked out their front door to se where the freight train was coming through, Had one hell of a shock when I touched the wires to the battery. I didn't use a relay I had just purchased them from a swapmeet and was testing them.I only had a 12 volt battery.

[Fordestes]

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when I use the horns I an going to ask some electrical guru what resistor I will need to connect them the correct way and drop them to 6volts.

[19Fordy]

When converting to 12V I used a 60 ohm resistor to make my stock 40 Ford BATT gauge operate on 6 volts. This may help.
https://www.fordbarn.com/forum/showth...rting+12+volts

[flatheadmurre]

The horn are a switch operated at a specific frequency so connecting 2 with different frquencys in series will not be working very good.
You get lower output and frequency cause they will "misfire" when one is open and the other doesn´t get any current.
Operating them at 12v for a short period will probably not burn them up but you get a higher pitch from them.
So a dropping resistor as stated above is the correct way.

[fordor41]

I connected my trumpet style '41 horns in parallel and ran them on 12V for years. Of course I didn't blow them for extended periods of time. Finally burned one out when I hit a large pothole in Ohio and the relay stuck. Thought they were going to blow the paint off the hood before I could get them disconnected!

[Drbrown]

Originally Posted by koates

Horns cant work connected in series, have to be in parallel. Either run them on 12 volts for a louder and rough out of tune sound or with a resistor in series with each horn to drop the supply voltage to 6 volts for the correct in tune sound. Regards, Kevin.

The horns DO work when connected in series. At least mine do. To add .... my horn circuit is on a 30 amp fuse. A member in the forums tested his 6v horn circuit and found it didn't draw more than 20 amps. If the relay or horns malfunction and draw more current the fuse will blow.

[Drbrown]

Originally Posted by Fordestes

I connected two 6volt horns to 12 volts in series by mounting on a wood insulator, had one a little louder so I switched positions and was so loud every neighbor on the block looked out their front door to se where the freight train was coming through, Had one hell of a shock when I touched the wires to the battery. I didn't use a relay I had just purchased them from a swapmeet and was testing them.I only had a 12 volt battery.

That's why a relay is used. Too much draw at initial connection i.e. like connecting a large motor. Relays help prevent "arching" at the connection point when heavy loads are connected.

[Drbrown]

Originally Posted by 19Fordy

When converting to 12V I used a 60 ohm resistor to make my stock 40 Ford BATT gauge operate on 6 volts. This may help.
https://www.fordbarn.com/forum/showth...rting+12+volts

Reducing voltage for gauges is generally different. However regarding horns there is a 2015 thread on Ford V8 which recommends a 0.5 ohm 50 watt resistor on the feeder if that's the way one wants to go.

[Drbrown]

Originally Posted by fordor41

I connected my trumpet style '41 horns in parallel and ran them on 12V for years. Of course I didn't blow them for extended periods of time. Finally burned one out when I hit a large pothole in Ohio and the relay stuck. Thought they were going to blow the paint off the hood before I could get them disconnected!

This I don't understand .... ? ? .... if the points in the horn, which are normally in closed position, "burned-out" it wouldn't work. But if the relay "burned-out" another words fused in its connected position, then the horns would sound continuously as described.

It was not uncommon in-the-old-days for a horn relay to freeze or malfunction, and the driver or mechanic would dash under the hood to pull the wires apart.

[Flat Ernie]

You can run the horns in series if one is electrically isolated. They will not be as loud as they could be. This is because they make/break each other's circuit, but it does help to keep the current down a little - start-up current will still be high though.

It is far easier to run them in parallel as original and have them be louder. If you still have a 6V horn relay, they are often better than 12V replacements because the contacts are often heavier. But I've found that aftermarket relays are better still.

The horns, which already draw high current, particularly on start-up, will draw double that on 12V.

I really like to find and use the 48-52 F1 dual trumpet horns - man are they loud on 12V. But most trumpet horns will be nice and loud. The other thing I like about the earlier horns is most are adjustable and the contacts can be cleaned. Pull the bell off the back and you can dress the points, replace any frayed wires, and adjust the tone/sound/volume.

[Flat Ernie]

Originally Posted by 19Fordy

When converting to 12V I used a 60 ohm resistor to make my stock 40 Ford BATT gauge operate on 6 volts. This may help.
https://www.fordbarn.com/forum/showth...rting+12+volts

The 60 ohm resistor for the BATT gauge is a calibration issue. Although the BATT gauge acts as a voltmeter, it is still measuring current. Consequently, it's important to know the resistance of the entire circuit - in this case, the Ford service manual gave us the 60 Ohm value, so we double it to keep the current through the gauge the same (most voltmeters are really measuring current, just calibrated to show voltage).

Originally Posted by Drbrown

Reducing voltage for gauges is generally different. However regarding horns there is a 2015 thread on Ford V8 which recommends a 0.5 ohm 50 watt resistor on the feeder if that's the way one wants to go.

Finding a high wattage, low ohm resistor is likely a challenge, but it might work - would need to know the impedance of the horns to say if that was the correct value or not. It's likely very close though, just by gut feeling...

[flatheadmurre]

How about a dropping resistor for an ignition coil ?
Is in the right range and should probably survive normal use...

[Drbrown]

Originally Posted by flatheadmurre

How about a dropping resistor for an ignition coil ?
Is in the right range and should probably survive normal use...

In my case that's an interesting question. Seem to remember that those OE coil resistors only drop the voltage from abt 6v to 3 or 4 volts - but I could be wrong. My OE Circuit Breaker with its 6v coil resistor are unused (my coil was changed-out for a 12v coil with internal resistor). I can run some jumper wires and see what my meter reports. I'd either need to go back to a 6v relay or put the resistor on the horn-side of the 12v relay. However, that OE is an open-air resistor and probably not suitable exposed in an engine compartment.

Flat Ernie: www.digikey.com/products-search .... an on-line company that offers wide range of resistor sizes and types, as well as other electronic items at reasonable prices and shipping for small orders. They sell a "Dale #RW-50 50watt 0.5 ohm which is encased/mountable abt 2 inches long.

[flatheadmurre]

I was more thinking about the modern ceramic square ones usually around 0.5ohm.
The voltage drop is depending on the current going through the resistor so one dropping 3v in one aplication can drop 1v in another.

[Flat Ernie]

I'd just run 'em on straight 12V. They're nice and angry sounding.

[fordor41]

Originally Posted by Drbrown

This I don't understand .... ? ? .... if the points in the horn, which are normally in closed position, "burned-out" it wouldn't work. But if the relay "burned-out" another words fused in its connected position, then the horns would sound continuously as described.

It was not uncommon in-the-old-days for a horn relay to freeze or malfunction, and the driver or mechanic would dash under the hood to pull the wires apart.

When I hit the pot hole the horns started to blow. I disconnected them at the relay but one horn was no good after that. I used the other horn for about 10 yrs after that happened.