The Stovebolt Site Forums The Shop Area The Electrical Bay wiring the horn

HI Folks,
I've been re-wiring my "51 "3800" panel and I can't figure out what to do with the wire coming out of the column. Ok; when you stop laughing, tell me. And...what is the horn relay for, and do I need it?
Thanks everyone,
Ed Lupardo

Well, here's the deal. 1951 wiring diagram shows no relay was used. The dual horn option used a relay. They did start using relays right after 1953.
Regardless, a relay is a good idea. The non relay designed truck's horn trumpet had two contacts and on newer designs there will only be one. You can use either trumpet design on a relay. Just wired a little differently.....so...........

Yes you do if you have an original style set up. For 6V or 12V yes.

That horn wire grounds the relay, which makes the relay (which is a switch) make contact inside. It closes contacts between the relay battery hot terminal and the output to horn trumpet terminal. Honk Honk.
So relay should have three terminals.... one for batt, one for horn trumpet wire and one for your column wire. They are sometimes marked "H" "B" "S" Horn Battery Switch. Post a pic of your relay on here using the attachment manager at lower left of your post.

The grounding I mentioned is done at the column horn button. Thru the various horn parts, you make that wire touch the column metal, which is battery ground. When you eventually send current to the horn trumpet, it causes a electromagnetic operated contact inside horn trumpet to open and close rapidly "vibrating" a diaphragm that sounds like a horn. Before that there was a motor inside horn operating a ratchet, like a playing card on bicycle spokes, only on a diaphragm instead.

This is the relay you may have? I don't know what changes you or a previous owner may have made. Adding a horn relay to a non relay truck is a good, no risk idea. But not for a purist I guess.

Did the 1953 truck single seashell-style standard-horn use a relay (as used with that same single standard seashell style horn in 1954)?

The 1953 dual seashell horns did use a relay; and, earlier optional/accessory dual horns used a relay.

The Master Parts Catalog is not clear on this.

What style horn do you have?
Trumpet style on a '51 does not use a relay.
Seashell horns do use a relay.
To use a relay with a trumpet style horn requires different wiring to make it work because the trumpet horn is not grounded (seashell horns are grounded). I just added a relay for my trumpet horn on my '49. If you decide to go that route (you don't need to do so in my opinion) I can take some pictures of my wires.

I can't use the term seashell horn. But I know what you mean. I call the noise making unit the trumpet. Diagrams do not give shape.
Cars used dual horns back to at least 49. They had relays and one terminal trumpets. Cars continued to use dual horns. Hi note/Lo note.

1938 seems to show one two-terminal trumpet, no relay.
1941 Truck diagram shows dual one-terminal trumpets with relay.
1942-1951 Truck diagram shows one two-terminal horn trumpet, no relay.

1952 Truck Wiring Diagram: Not found

1953 and 1954 truck diagram shows one one-terminal horn trumpet with relay.

Do not know about or see any wiring diagrams regarding horn options for trucks.

Engineers decided that it was better not to be "shorting out" an actual circuit at the horn button (big amps)(spark-spark). So using a one terminal trumpet, they grounded it's case thru it's mounting hardware. Let a relay provide power to the trumpet terminal, and just let the horn button energize an electromagnetic coil inside relay at "S" (low amps)(no spark), which closes relay contacts "B" and "H" (big amps). No more buzzing your tooth fillings when you honk.

I apologize for using the term "sea shell"; I'll use either "snail-shell style" or "trumpet style" in the future - in an attempt to clearly distinguish the two styles of horn bodies that GM used on old "Stovebolt era" trucks (at least from 47-52).

In older (pre-1947) parts manuals, GM used the term "projector" for the output piece and the term "backshell" for the part/parts behind the "projector" on both styles of horns.

The GM illustrations that I have only show the two (snail-shell) horns in 1947-1952 sales/data-book illustrations.
No relay is displayed (or stated/referred-to); however, a horn relay was available for horns from 1934 onwards.

Before 1947, a long straight-neck "trumpet-style" horn was available as optional equipment. It is not clear what style, if any, standard-equipment horn came with these older trucks.

Maybe Brad or another member has installation instructions for the pre-1953 (47-52) GM accessory dual "snail-shell style horns"?
The installation instructions would show the relay, if it was provided/used prior to 1953 (my guess is that a relay was provided with those dual horns?).

Back to Ed's original post/question: a relay was not used as standard equipment with a single horn in 1951; however, a relay was available as an accessory. It will not hurt (and, it might help).

Thanks a million Tim for your good information

Thanks so much Bart for the info. I'm on my way to the garage.

Too much focus on shape for an electrical question. Tried to talk "terminals" and their hook up, on that thing that is not a relay, with regard to year of truck. I agree on various shapes and their names, but that was not my concern in answering the posters question at first, then I was getting into Tims question about 53/54.
Anyway Ed, let us know if it eventually honks. At least you now know what it takes to make it work with TMI thrown in.(by me)

Bart,
I'm back. Please dumb this all down; way down for me. I get it that the wire coming out of the column is a "ground". What I cannot wrap my head around is...
what "powers up' the column and where?
I understand that the horn button is a switch which closes the circuit when you press the horn button and the horn beeps; but where does the power come from?
Thanks in advance pal.
Ed

Any pics or further explanation would be helpful Carl.
Thanks

vintage, the power for the horn comes from the "other side" of the horn (typically the horn relay) or from battery power. The horn "switch" CLOSES the horn circuit to ground.

What style of horn are you using? If it is the standard trumpet style, you will not need a relay. All you need to do is run an always hot wire (original source is at the ammeter) to one screw on the back of the horn, and the wire coming from the horn button wire on the steering mast to the other screw on the back of the horn.

Hi Ed, You don't need a dumbing down. You are no dummy that's for sure. I will explain the way I would like it explained to me. Without all the science. All I can give is the way I see it,

Not going to get into physics or electrons or neutrons or morons. Not going to discuss why we say electricity travels from positive to negative, but that really it is the opposite. It went too many years with that theory until science proved it wrong. DOES NOT MATTER when discussing simple DC truck wiring. I'm always going to say is flows from the battery positive to ground (neg).

Current flows from the battery to and thru "loads". Bulbs, motors, horn. On our trucks everything has a switch to turn the flow on and off. This flow must have a "return" path. (not talking home voltage, that's AC). On our trucks, the return wire is the whole truck and all it's current carrying metal.

The horn is sort of unique. Most switches on our trucks are letting positive voltage thru to a load and back thru the chassis. (Everything should pass thru a fuse of some sort). Lets call the way a horn diaphragm vibrates, "a load". It's not a bulb, not a motor, not a solenoid not a radio. I explained how it works. That too, it not important. It's a "load". I.E......something that uses the battery power.

Some older horns were wired with a wire from the battery/ammeter to the horn. Thru the load and back out another wire to the horn button. So where is the switch? Well, on this type horn we complete the entire horn circuit by closing the ground path at the horn button. This is the circuit style Carl is speaking of.

Then it was decided that closing a high draw "load" at the column was not good.
The horn is a good size amp draw. 10+ amps. 12 ga wire is used. Converting to 12V could affect draw. Switching a big draw at the button, with a disc and a plunger, wasn't the best switch. There also was a big voltage drop to the horn. The use of a remote relay supposedly shortened the wire. On the dual horns back then, they used a relay.

So on newer (about 1954) single horns used a relay. Solving several minor issues as above and eliminating an "always hot" horn terminal.

The relay has a low amp draw, electromagnetic coil inside. When you now ground the return path, you are just causing a magnet to close a set of big amp carrying contacts (the actual horn switch), which are also inside the relay. When that coil causes that switch to close, it connects voltage from the battery to the relay, thru those big contacts, out the relay to the horn. But then the horn "load" needs a return path with just that one hot wire going to it from the relay. So the horn is built with its return path thru it's own body, thru it's bolt, into the chassis and back to the battery which completes the circuit.........honks.

This electromagnetic coil get's power from the battery. The power input to the relay is split into two different circuits. One to the coil, thru the coil and out thru the relay's mounting screws into the chassis and back to the battery. This is very close to a starter solenoid. That is why it's called a switch by some vendors. Even called a relay. Ford used a separate starter relay

The other circuit is to the horn as explained.

Bottom line is the relay is the horn switch and the button is the relay switch.

ED, please answer what type of horn you have or how many terminals it has. So we can focus on YOUR horn hookup.

tclederman is correct (again), the later shapes were called Sea Shell, the older were call Klaxon. Delco-Remy got into the horn business in 1924 with the purchase of the Klaxon Horn Company in Newark, NJ.

Bart,
I took 2 6V horns from a 53 chevy car and wired them into my system. These are single wire horns; self grounding. I used them because when I send 12V through them, you can hear them at your house.
So...knowing that, what do you suggest?
I'm so grateful for all yours and Carl's advice.
Ed

For a self grounded horn, you should use a relay. Wire power to the relay common contact, from the relay NO contact to the horn. Wire power (a jumper) to one relay coil contact and the other relay coil contact to your horn button (assuming its the stock horn button, which supplies a ground). Be sure to put a fuse on the power wire to the relay.

Get THIS relay or equivalent. Terminals are marked "battery" "horn" "switch".

1. Mount relay in a good spot on inner fender or firewall. Be sure it's mounting feet touch bare metal.
2. Wire from always hot fuse to "battery" terminal.
3. Wire from "horn" terminal to horns. Jump from one to the other or splice.
4. Wire from column to "switch" terminal.

To add to what Bartamos said.

I bought that exact switch from Classic Parts a few months ago and mine was labeled 1, 3 & 5.

1) Horn
3) Battery
5) Switch

Good point. Many of them just have a schematic imprinted on them. They want to market it for more than just horns.

I just installed the horn relay and my horn works. That was exactly what I needed. Thank you everyone for the excellent information. You guys are the best. You have no idea how happy I am right now.
Ed Lupardo

Bart,
Just installed the relay and I have a horn!! You are the best pal. Thanks so much for all your time and expertise. I'm very grateful.
Ed Lupardo

That makes me happy too. Good work Ed.