I got some aftermarket horns off a Volvo at a junkyard. They have only one terminal on each horn. What is the correct way to wiring this type of horn. Do they need a relay. I tested them without any relay in place, just the horns themselves wired like they were on the donor car. They would work at first, then intermittently, then not at all. My wife was holding the horn button down while I fiddled around with the horn wiring to see if I could find a loose connection. She says she saw a wisp of smoke come up out of the dash. I didn't see it and could not smell anything. I'm hoping she just thought it would be a quick way to end the work session. I sure hope she didn't see smoke. No fuse blew. Anyway, I need help. I didn't even check the donor car for a relay. What's the deal with these single-terminal horns? Could I have damaged some wiring by wiring them without a relay and trying to test them by having my wife hold down the horn button?? Is this odorless smoke she saw just 'smoke and mirrors" to get back in the warm house from the cold garage?
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.

Hi Doug -

The horns are wired so that the contact on the steering wheel completes the ground side of the circuit.

Power from the fuse panel #2, also w/s wipers. Thence out front to the horns. They are wired in parallel. All the wires, hot or not, are black.

Hot wire to left horn, a jumper over to the right horn. Ground wire from right horn to left horn to inside the cabin - to the steering wheel.

No relay in the circuit.

What you found in the boneyard is a non-Volvo system, where the horn contact completes the hot side of the circuit. The circuit engages a relay, which then allows battery current to get to the horns. The horns are grounded to the frame via the mounting bolts.

Test the horns off the car. I would just put one up near the battery and use a pair of test leads. When the horn blows, (1) it'll be louder than you expect, don't jump too high, (2) it might vibrate and fall off whatever you have it sitting on. Be ready. Test both.

The horns may draw more than the Volvo design current. That may have messed up the horn circuit, but if the fuse is OK, Hmmmmmmmm... dunno about the smoke. Put a test light in where the horn is connected and see what it does.

You may have to use a relay due to heavier current draw. Get one from a donor, and include the base. cut the wires to the base so as to have plenty of length to hook up to. The central locks, power windows, or - on an 83 or 84 240 - either of the fuel system relays.

Post back with your test results, OK?

Good Luck,

Bob

:>)

Thanks Bob, Here are a couple more clues.

I tested the horns at the junkyard, after removing them from the car. They worked well with twelve volts put through them with one wire to the terminal on the body of the horn and the other wire to the mounting bolt of the horn.

The horns were mounted on the donor with nonconductive mounting brackets. They were not grounded to any metal of the car up near the horns. I mounted them the same way on my car. If I jump a wire from the mounting bolt of one of the horns to the car body, the horns sound when I turn the key on without pressing the horn button. Not good.

What seems to be happening is that they'll work fine, but only for a while. After a few beeps they sound sick for a bit, you can hear them trying to beep but just sounding sick instead, then they won't sound at all. Last night when they quit, I waited ten minutes, and they worked again. They work this morning too.

My main fear is that I don't want to melt the insulation off of any wiring in the system, particularly in some hard-to-reach place. I'm wondering if I should check the contacts under the two horn buttons that this car has. Do these buttons just pry off. It's 1981.

Also, I'm headed back to the junkyard for a closer look at the donor. It very well might have a relay mounted somewhere that I didn't see. Heck, I didn't even look. Auto electric is not my strong point, to say the least.

Thanks a lot for the help. I really appreciate it. Please post back with any more ideas or suggestions.


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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.

Doug -

See if this helps:

You say:
The horns were mounted on the donor with nonconductive mounting brackets. They were not grounded to any metal of the car up near the horns. I mounted them the same way on my car. If I jump a wire from the mounting bolt of one of the horns to the car body, the horns sound when I turn the key on without
pressing the horn button. Not good.


I said that the system is wired so that the horn button closes the ground side of the circuit, that the hot side is always connected to the horns and is hot when the key is turned.

So when you connected the horns to the Volvo wires, that must have been the hot side. Then the jump of a wire to the frame closes the ground side and the horns sound.

Yes, you may be overheating the wiring, depending on how much power the horns demand. Having 12Volts is good, but not all you need. Heavier wire is needed to carry heavier current. Like a water hose - you can have the same pressure (voltage) in a 1/2 inch hose and a fire hose. But you can see which delivers more water. The volume is analogous to current or amperage. Heavier wire.

With water at too-small hose merely delivers less. With electricity, the smaller wire heats up and can create problems. In your house, the gauge of the wire in the walls is related to the amp level of your circuit breakers. A 20amp breaker can handle 12 gauge wire. If the breaker is 15amps, only 14gauge is legal or safe.

Back to your horns. You will need a relay, period. Get one of the little cube-shaped ones, and its base, and a goodly length of wire to the base.

Overview: The relay is an electrically operated switch. You will need it set up so that when the horn buttoin is pushed, the relay closes, and no power is sent to the horns. The contacts in the relay close and that allows power to flow to the horns.

Most relays have standardized terminal numbers, and some have a little diagram on the side. That's handy.

Get a relay and base, post back and tell me what the wires are. Look at the bottom of the relay for the terminal numbers, then figure out what color wire goes to it. The numbers needed are #85, 86, 87, and 30.

Also look a the wires connected to the Volvo horns. Is one black and one yellow? Somewhere between 1978 and 1984 the color changed from all black to SB and Y. The Y is hot with the key turned. SB (Swedish for black) is ground side, it goes back to the steering wheel.

You should not have to do anything with the steering wheel contacts, just don't test again. Overloading might tend to burn them and why add labor?

Good Luck,

Bob

:>)

Bob,

Here's where I am on this horn deal. I'm sure everything is wired just like it was on the donor car. I checked to make sure the dielectric grease I had put on the hot horn terminal connections wasn't somehow bleeding the current to the exterior of the horn bodies. But just like the name means, the dielectric grease doesn't conduct electricity. So, all I can figure is that the horns have an internal short conducting electricity to their metal bodies. They sound great, though, for the short beeps I've put through them. It seems out of whack to be driving around with these two metal horns that are hot whenever the key is on. The first time one of them loosens up or gets grounded in any way, the horns will be blaring away. Sounds like maybe I ought to head back up to the boneyard and grab that nice pair of factory horns of that 87 wagon I saw. What do you think?
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.

Did not read the BB Wednesday - great weather for outdoor work!


So you have the WDM (not weapons of...) for the 1985 240, right?


Makes it easy, since I cannot yet put in wiring diagrams and pictures.

The horn donor car I am assuming is not a Volvo 240, right?

OK. All horns need two connections to work, (duh?). Volvo connects two wires to each horn. Your donor connects only one wire to the one terminal, and uses some other way to connect the other side. The horns don't care which terminal is positive or which is negative.

Test the boneyard horn. Test wire terminal to the battery positive, and then a test wire from the battery negative or a nearby car frame ground. Then touch that wire to various parts of the horn. The mounting bolt, the body of the horn, etc.

I expect that the mounting bolt will make the horn sound.

Most all horn insides are such that one side of coil is connected to the horn body. In a volvo, the terminal for that side of the coil should get the black wire. The other terminal gets the hot connection and the body won't be hot all the time. Use an ohmmeter to find 0 resistance between the horn body and one of the terminals. Mark that terminal somehow.

The non-conduction mount might be just for insulating the horn vibration from the car body.

If you like the sound of the donor horns and want to have them, we can work it out, relay and all.

The five-terminal relay will work, so will a four-prong relay. Save the five-prong for another application. Is there a little diagram on one side of the cover?

Look for a little coil-looking thing. Terminals 85 and 86 go to the coil. Connect 86 to 12volts, then 85 to ground and the relay CLOSE with an audibe click.

Whatever is connected to #30 will be connected to #87 when the relay is OPEN, and #87b when it is CLOSED. Check this with a ohm meter or test light, there are some which are different.

From the location where you got it, you may have the relay used for the key-out headlight cutoff feature that began in 1986. You may want to retro-fit your Volvo with that, I enjoy it.

Did you get the base of the relay? What wire colors go to which terminals?

Post back here - so others can benefit from this conversation. Then send me an email so I'll know to go look.

Good Luck,

Bob

:>)

Bob,

I don't have the WDM for any of the Volvos yet. I just ordered one for 1981.

The donor car for the horns was indeed a Volvo, a 1983 244. They are aftermarket horns, though, made in Italy by Stebel.

I removed both horns from the car and tested them on the bench with a spare battery. I can hook up either negative or positive to the single terminal on a horn and make it sound by touching the other wire from the battery to any metal on the horn body. It doesn't make any difference whether I touch the second wire to the horn mounting bolt/post or anywhere else on the metal part of the body. There is continuity from the single terminal on each horn to all other metal on the outside of that horn. If the PO had not mounted them with non-conductive material, they would sound whenever the key is on.

Am I missing something here? Crazy horns?

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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.

No, they are not crazy horns, just made for a car with positive ground, and the Volvo system uses negative ground. The PO did OK at hooking them up.

Inside the horn is just a coil, it makes a vibration that is connected to the diaphragm which makes noise. One wire from that coil goes to the single terminal, the other is just attached to the horn body. So we'll treat the mounting bolt as the "missing" other terminal.

Connect the yellow wire to the single terminal. Then fashion a way to connect the black wire to the mounting bolt. That ought to work. Connect one horn, test. The horn should work even if not mounted on the car.

when the key is on, the horn body will not be hot. If the body, or mounting bolt, touches a ground, the horn will sound. That is the connection that is made in the steering wheel, as the Volvo system is designed to to.

There should be a size of female connector that will plug onto the male connector inside of the rubber cup that surrounds the volvo harness connector. I get the little spade lug connectors from the corner ACE hardware, it's closer than Radio Shack.

There are a number of sizes and insulation styles. The wire size is probably 18 or 16. Get the fully insulated type, female, .250 wide. (I think the horn harness has a male connector, but you check.)

Use a short wire, one end in the harness connector and the other end attached to the mounting bolt, and you should be good to go.

Lemme know how it goes.

Good Luck,

Bob

:>)

Bob,

Addition to last post: I'm figuring these horns must have an internal short to the case and that's why the outside of the cases are hot whenever the key is on. I'll double check things tomorrow when I'm not so tired and let you know. They may be toast. Thanks.
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.

Bob, Thanks for the very helpful thorough post. I checked a few more things:

Yes, the wires to the horns are black and yellow, and the yellow is hot when the key is on. In fact, the entire outer surface of both horn bodies is hot when the key is on. This doesn't seem right to me. Sounds crazy to have the whole outside of the horns hot whenever the key is on.

I looked through the half dozen relays I have here at the house. The closest one I have to what you describe is a metal cube shape, one inch wide in two directions and 3/4 inch the third dimension. It has five terminals: 30, 85, 86, 87, and 87b. I got it from an 87 240 in front of or above where the driver's feet would be. I don't know what it was originally for on that car. I don't even know if it works. I can chase down another one that has just the four terminals you mentioned if that would be better. This one is a Bosch 0332015012, (12V 2x15A).

The horns work now, but I'm not going to do anymore laying-on-the-horn type of testing until I get it wired right. With the relay installed, would that mean that the heavy current needed to run the horns correctly would only run from the relay to the horns, with a much lighter current from the horn button to the relay so I wouldn't have the wires in the steering column heating up?

Thanks for your help. It's about time I learned more about relays and wiring. I don't know how to wire the relay, but if you explain it, I'll get it done. My E-mail is good too, if we shouldn't be loading the board with too much back and forth stuff.
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Thanks to everyone for the help, Doug C. 81 242 Brick Off Blocks, stock, M46; 86 244, 140k , auto.