spooker

12Volt to 6 Volt Resistor for 1936 Ford Horns

Recommended Posts

MY 36 Ford has been upgraded to 12v, but they forgot the horns which complain from the higher voltage.  I have found that resistors are available, but need to know what ohm resistor is needed to reduce voltage from 12 to 6 for the two horns.  Thanks, Spooker. 

Share this post


Link to post
Share on other sites

What you're looking to build is called a voltage divider, 12v is divided into 6v by placing two resistors same ohm rating in series, that is end to end and tapping Into the middle for 6 volt supply. Have no idea how much juice a horn from a 36 Ford will draw, but electricity will always take the path of least resistance, so measure the horn resistance and get a couple 5 or 10 watt wire wound resistors with slightly to moderately higher resistance than the horn, hook them together and tap the middle. Radio Shack sells wire wound two packs for about $3 and so long as you don't horn crazy and lay on the horn button down for minutes at a time, there is no need to design the perfect series parallel circuit.

Share this post


Link to post
Share on other sites
1 hour ago, jp928 said:

Is it that hard to find 6V horns of the period?

 

jp 26 Rover 9

 

The OP would need 12V horns from the period, which I suspect ARE hard to find.

Of course, non-original 12V horns are plentiful and likely cheaper than a voltage reducer...

Share this post


Link to post
Share on other sites

A single resistor between the horn wire and the horn should suffice (The horn itself will act like the lower portion of a voltage divider). Since I don't have the horns here to measure, I made some assumptions. A two or three ohm resistor rated at 5 watts should drop the voltage to about 7.2 volts. Radio shack does not offer a single two ohm resistor but they do offer a 1.0 ohm two pack as a 10 watt wire wound. The 10 watt rating is overkill, but adequate for a short duration load like a horn:

https://www.radioshack.com/collections/resistors/products/radioshack-1-0-ohm-10w-10-wirewound-resistor-2-pack

 

These are ceramic encapsulated high power rated capable of handling the estimated 2 amps. Put the two together in series.

 

An alternative is to seek a single three ohm wire wound resistor from a specialty supplier such as Mouser:

http://www.mouser.com/ProductDetail/Ohmite/805F3R0E/?qs=sGAEpiMZZMtlubZbdhIBICSp%2fklkKtPZETBpMRIlZ6U%3d

 

If your intent is to hide the resistor, this cement version maybe easier to conceal inside some shrink tubing:

http://www.mouser.com/ProductDetail/Xicon/280-CR5-30-RC/?qs=sGAEpiMZZMtlubZbdhIBIL0b62albrSmwGHhczINzvU%3d

 

Don't forget to solder the connections.

 

Share this post


Link to post
Share on other sites

Forget the resistor!

It is a very poor solution.

Jump on to eBay and search for a "12 volt to 6 volt step down converter 60W".

You can get them out of China or Hong Kong for about $8.

That will give you 10 amps at 6 volts which is ample for your horn and fuel gauge. 

  • Like 1

Share this post


Link to post
Share on other sites

Ahhhh........ , just take the easy way out and wire 'em in series rather than parallel , assuming there is a ground lug , and not grounded by way of the horn body. In that case the latter might not end up being the easy way , but is it worth a look ?  - Carl

Edited by C Carl
Clarification (see edit history)

Share this post


Link to post
Share on other sites
43 minutes ago, C Carl said:

Ahhhh........ , just take the easy way out and wire 'em in series rather than parallel , assuming there is a ground lug , and not grounded by way of the horn body. In that case the latter might not end up being the easy way , but is it worth a look ?  - Carl

 

If there are two horns then this would be the best solution IMO as well.

Share this post


Link to post
Share on other sites

Some of the better horn sounds are produced by using two horns with different but complementary tones, a bit like playing chords on a piano. You would not normally notice this until one of them failed.

I will see if I can any data on this.

jp 26 Rover 9

Share this post


Link to post
Share on other sites
On ‎1‎/‎28‎/‎2017 at 1:18 AM, lozrocks said:

Forget the resistor!

It is a very poor solution.

Jump on to eBay and search for a "12 volt to 6 volt step down converter 60W".

You can get them out of China or Hong Kong for about $8.

That will give you 10 amps at 6 volts which is ample for your horn and fuel gauge. 

BEST IDEA YET................

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now