Horn honks with 12v from a battery, but not 12v from horn connector

Well the horn in the Samurai died, probably from submerging it a few times. I know it's the horn because I get 12v at the connectors that plug into the horn itself.

No big deal, I pick up a new one, 10 minute job right? The new horn is actually a pair of aftermarket horns, they say they require a 15A circuit (the two are wired in parallel) which is what the old horn used. So I wire one up and...it clicks. Not any relay but the horn itself. Tried wiring it the other way just in case, same thing. Tried running the engine in case there isn't enough power or something, same thing. I took a jumpstarter battery and touched the terminals and it honks.

Why is the power at the horn connectors so special that it can't make these horns honk?

You got volts. Do you have amps? Put your voltmeter on the horn connector and see if the voltage drops a bunch.

So I should try measuring the voltage at the horn connector when the horn's hooked up, and see if it drops (to less than 12v?) when I hit the button?

Edit: Wasn't sure what you wanted me to do so I ran tests with the voltmeter both in series and in parallel with the new horn and measured the voltages while hitting the horn button.

In series: 12-13V In parallel: 0-4V

Is there power at the horns all the time? If so, it probably grounds at the steering wheel, and you have a bad ground. Is there only power there when the horn button is pushed? It will have a relay providing power, and the body of the horn will be grounded.

Either way, I think you need to look at the ground side of your circuit.

There's only power when I press the button. When I tested the horn with the jumpstart battery it worked on a wooden chair, so I guess the body doesn't need to be grounded (the instructions don't specify this either).

Streetwiseguy wrote: You got volts. Do you have amps? Put your voltmeter on the horn connector and see if the voltage drops a bunch.

I use a bulb to check for amps, if you have enough amperage to light up a standard automotive bulb nice and bright it should power whatever you need.

does the Samurai have a clock-spring in the steering column ... ?

Think Streetwiseguy was on the right track. You say the new horns require a 15A circuit, does it have that? Multimeter switched to amps would tell you. If you don't have a multimeter then what psychic_mechanic says will work in a pinch. Check the fuse for the horn circuit and see what it is, that should also tell you. But your check in parallel seems to be a culprit also. Seems the horns might be designed to be wired in series if the voltage drops that much in parallel. Then again working on a wooden chair and not in the car, wonder if insulating the mount with something like rubber or plastic would prevent it from grounding out. Just thinking here.

Do you have an aftermarket steering wheel? I had problems in the past, especially with Grant wheels. I couldn't get the horns to work reliably no matter what I did.

I'm using the stock steering wheel and the fuse for the horn circuit is 15A (although something else is on it too...the dome light IIRC).

I don't know if there's any kind of spring in the steering column. I don't have a DC ammeter so I'll try the bulb test.

When I tested the horn in the jeep, I tried it both with the body of the horn grounded and ungrounded, it didn't work either way.

The wiring diagram that came with the horns definitely shows them being hooked up in parallel.

I think I'll just have to use the existing horn connector to power a relay and put the horns on a new circuit. It might be a quick fix but I have to get the horn (among other things) fixed for this weekend.

Oh also I tested the old horn with the jumpstarter battery and it's definitely dead.

Got it running last night by using a relay and running a new circuit. The stock horn circuit doesn't use a relay at all.

I'm resurrecting this thread because now I have another weird problem with the horn.

So after I first got the horn fixed, I did an event, and the next day I noticed the horn was dead. I got a total of under 4 seconds of honking time out of it. After running some tests I found that the relay was bad - it just stayed off all the time. Well it was an old relay I had in a box for some time, maybe it was a fluke.

So next weekend the exact same thing happens. I put in a relay, do the event with no problems (horn didn't sound so good at one point, but I did sorta submerge it...) and by the time I was finished the horn was dead. I haven't really had a chance to check it out with an electrical meter yet but when I press the horn button the relay doesn't click.

What could kill a relay like this? I don't think it's dust or water because there's an identical relay for the electric radiator fan mounted right next to it that's been working fine for probably over a year now. Both are identical 30A relays, and the one the horn is on has a 20A fuse in it.

I'm still thinking ground issue - but I had an old bronco with a fiberglass body - so everything wiring was a ground issue.

Alright, You didn't mention the year Samurai, so I used '86 to plug into Mitchell.

The circuit starts at the fusebox and supplies 12v to the hot side of the horn. The other side grounds through the horn switch, no relay.

Take out all of the modifications you did. Bust out the multimeter again and ground the black lead to the battery negative, and check the 12v side of the horn. It will probably read 12v at rest, if not check the fuse to see if it's almost blown, corroded, or loose. You get the point, I'd just swap it anyway for the same value.

So if it read 12v at rest, honk it. If it falls on it's ass, like less than 6v, check all that stuff I said before, the problem is on this side of the horn.

If it pretty much hangs at 12v at rest and honking it, take the red lead of your meter and hook it to the positive on the battery. Now take your black lead, test the negative side of the horn, and honk it. Chances are if you've made it this far, you've got less than 6v, so now you get to check the slip ring (which is in the column), and the horn switch itself. Check for obvious things, and if you are certain which wire is the horn, jump the front and the back sides of the connections. You can diagnose better if you break it down into sections.

Let me know what year you have and I can look up more specific information. BTW, in all my years of wiring, relay failure is extremely rare.

later, matt