Wiring new horns
 

I bought two new horns and went to mount and wire them up and ran into a problem.

On the new horns, one terminal is grounded to the horn body. So with the horn mounted on the fender, it is grounded. The brackets I have to mount the horn to the fender, do not have any insulation that would prevent the horn body making an electrical ground with the fender.

Wiring diagrams shows 2 wires going to the horn. The horn button is the electrical switch that grounds the horn to make it beep. But with the horn mounted it is grounded already so the horn would beep immediately.

I am wondering how it was done back in 1935. Is the horn bracket some how isolated with rubber washers so it did not ground the horn?

Or maybe the horns back in 1935 were not grounded to the body of the horn?

I thought I could put in a horn relay and just run a single wire to the horn since it is already grounded through the body. But I thought I would post something here to see what others have done (or what I am doing wrong).

PS The horns did not come with any wiring instructions. Nor did the mounting brackets (if I am supposed to use some insulating washers).

Thanks
Rich

Re: Wiring new horns
 

Here's a schematic with a horn relay....Would be positive ground for 1935



https://proxy.duckduckgo.com/iu/?u=h...png&f=1&nofb=1


Here's a schematic without a relay >


https://external-content.duckduckgo....jpg&f=1&nofb=1

Re: Wiring new horns
 

1935 Ford Wiring Diagram >


https://external-content.duckduckgo....jpg&f=1&nofb=1

Re: Wiring new horns
 

To answer your questions, the 35 horns were not grounded (see 35 diagram). One of its leads (yellow) was a direct connection to the battery, while the other (BLackYellow) was grounded through the horn.

The post 1935 horns did what you suggest; running through a relay to power the horns, as the first schematic shows. However the 15 amp fuse is too small. The 6 volt horns draw almost 10 amps each. Ford did not fuse this circuit, but a 30 amp fuse or circuit breaker would be safe feature.

Re: Wiring new horns
 

Perhaps a simplified wiring diagram may help. One wire is hot the other is the ground wire activated by the horn button.
https://www.fordbarn.com/forum/attac...6&d=1576163385

Re: Wiring new horns
 

18 gauge wire is too small even for 12-volt. The fuse is to protect the wire. Wire is gauged to carry the load so the fuse would have to work with the wire size used.

Horns do draw a lot of amps but it is an intermittent circuit. Folks generally don't activate the horns more than just a quick sounding. All the old Fords used the ground path to activate the horns. They didn't want a short inside the switch rod so they avoided power in there. The power generally comes from a position as close to the horns as possible so that wire resistance is minimal. The relays came later to simplify things so folks would get shocked when they sounded the horns. The relay reduces the current flow in the activation circuit & puts it all in the relay to horn circuit.

Re: Wiring new horns
 

Thanks guys for the quick response and information.

I am going to order a horn relay and run one wire to each horn. This solves a second problem. The hole in the bolt holding the bracket to the fender was too small to get the two horn wires through.

Now I just need to trace the wiring to figure out which wires to use and where to mount the relay in a convenient location. My wiring is so old and dirty it is impossible to tell their colors. Time to pull out the ohm meter to trace the wires.

Thanks again for the quick feedback.

Rich

Re: Wiring new horns
 

Sounds like it is time for a new wire harness.

Re: Wiring new horns
 

For power, wire it from the battery side of the voltage regulator or from the hot side of your fuse block. The hot side of the block would make it easier for installing a fuse block or circuit breaker inside the car. You would still have to search for the BLY (Black with yellow tracer) common out of the bottom of the steering column for the ground to the relay. If you still have the old wiring where the horns should be, one of them should be hot while the other should read minimum ohms when pressing the horn button.

Re: Wiring new horns
 

Ford wired it up directly from the battery connection on the starter solenoid. I would stick with that setup. The 38 wiring diagram is a good example. I also posted a VanPelt image of a horn relay (his site is also a good source for wiring diagrams).

Re: Wiring new horns
 

Js not for a 38 truck or at least with the little one horn setup, on a 35 no relay is needed. But can't hurt. This is a new set of horns, so no idea or suggestions.

Re: Wiring new horns
 

The horn relay has been ordered and already shipped. I should have it soon.

I have found the hot lead and ground lead from the horn button for the right horn. I should be able to find the same two leads for the left horn. I considered a new wiring harness, but did not want to tackle that job just for this issue. I reserve the right to change my mind in the future, ha ha ha.

Re: Wiring new horns
 

With electricals, keeping things simple is always the best idea. The horns are going to be connected in parallel no matter how you look at it. One wire will power both horns with a jumper between the two and same for ground path. Two extra wires for each power connection isn't necessary. The grounds can go to the nearest convenient attachment. I'd use at least 16 gauge for the relay operating circuit if it's 6-volt. If you want to fuse it you won't need more than a 10-amp fuse. It only powers the relay so current needed is not that high. The relay is where you need your horn switch to connect and circuit power can come from the same power that the horn comes from or use a jumper with a fuse in it.

The the horn sounding circuit from the relay to the horns can use 14 gauge for an intermittent circuit. You won't need a fuse since the only time it has power to it is when the horn is sounding and that is usually just momentary. A fuse for it would likely required at least a 20 amp but I wouldn't use one for the simple reason that the in rush current is high so it might blow the fuse. A circuit breaker would make more sense since they won't heat up as fast and if they pop then the circuit will come back as soon as it cools down. Like I mentioned, most folks don't lay on the horn all that long. A second or two at the most is usually all that is needed. There is hardly enough time for a wire to get hot.

Re: Wiring new horns
 

Update:
Thanks for the feedback / comments. The horn relay is installed and wired to the right side horn. Works like a champ. Left side horn will be installed as soon as it arrives.

I appreciate all the info and advice.