Horn doesn't work

[mgFray]

Was wondering if someone had a point to diagnosing what might be wrong with the horn on my M998.

I looked in the service manuals and didn't see any flow charts on checking the horn wiring.

So far, I've checked AT the horn. I've got 24V where I should. The other line has no voltage (or -). I tried to check it with someone pushing on the horn button and nothing changed.

Wondering what I should do next? I assume at this point either the horn switch isn't grounded property, the horn switch is bad, or the column connection is bad, or the wire from the column to the horn is bad.

 

[Action]

Turn the lights on?

 

[mgFray]

There is no power to the 24V line unless the lights are on.

I've had no horn since I bought the rig, and as I said, best I can tell it's not getting ground (-), but is getting 24V.

 

[Milcommoguy]

You answered your problem in the last statement
Wondering what I should do next? I assume at this point either the horn switch isn't grounded property thru the wiring, up the column, to the button, thru the button when activated with the return ground at the column, with a wire attached to the column making sure it is grounded. or the horn is bad?


Just saying. Light switch to SERV RUN, pull leads on horn. Find the one with 24 volt to ground. I think it is #26 ?? Reconnect to horn. Use a short test jumper to other horn connection to ground and be ready for "beep beep". Follow your last statement to remedy the issue.

Funky horn button can be a problem, CAMO

 

[Bulldogger]

My horn didn't work at first. I jumped 24V to it straight from a good source, bypassing the button. It crackled to life after some intermittent grumbles and has worked fine since. Try giving it a jump start!
BDGR

 

[TOBASH]

My horn didn't work at first. I jumped 24V to it straight from a good source, bypassing the button. It crackled to life after some intermittent grumbles and has worked fine since. Try giving it a jump start!
BDGR

Interesting.

 

[Mogman]

My horn didn't work at first. I jumped 24V to it straight from a good source, bypassing the button. It crackled to life after some intermittent grumbles and has worked fine since. Try giving it a jump start!
BDGR

The 24V does not come from the button, the button is the ground side.

 

[Mogman]

Was wondering if someone had a point to diagnosing what might be wrong with the horn on my M998.

I looked in the service manuals and didn't see any flow charts on checking the horn wiring.

So far, I've checked AT the horn. I've got 24V where I should. The other line has no voltage (or -). I tried to check it with someone pushing on the horn button and nothing changed.

Wondering what I should do next? I assume at this point either the horn switch isn't grounded property, the horn switch is bad, or the column connection is bad, or the wire from the column to the horn is bad.

Like you and others have mentioned, it could be the button, you can pop the button out after removing the snap ring and try shorting that lead to ground, there is also a ground wire to the steering column that could be "broken" so use a good ground then if it works try grounding the lead to the steering column itself.

 

[Mogman]

OK, I just woke up,,,,
There should be 24V on BOTH sides of the horn until the button is pushed, if you only have 24V on one side the horn is open (bad)

 

[Coug]

Since it's harder to check with the wires hooked up, find the hot wire, make sure that one is plugged into the horn. You should still see 24V on the other horn wire because as pointed out above, the horn button is just a ground.

If you have voltage coming out of the horn, try grounding it and seeing if the horn makes noise.

Sometimes corroded electrical connections will show voltage, but not allow any current to pass. Or the horn could be internally shorted allowing you to see voltage on the output but not actually work.

 

[papakb]

Take a look at the side of your steering column up under the dash. You'll see a connector on the side that's the ground return line from the horn. If you ground that connection and the horn blows your wiring is OK and the problem is in the colums or the horn button itself. There's a beryllium spring contact inside it that makes contact with the lead running up to the button that has a habit of breaking off. It's easy to replace, just 2 screws. The new one comes with a little tube of grease to lubricate it. If that's good then the problem is the button itself. Corrosion can cause it to not make contact with the steering wheel. Again, an easy fix, just a simple retaining ring that will let the button slip out of the steering wheel after it's removed. You can check the buttom with a multimeter to see if it's still makes contact between it's lead and the buttons case. This is the same horn button used in the 151 but it's only got a short wire on it instead of the long one used in the jeep. Easy to shorten up if you have one.

 

[mgFray]

thanks, I'll start with the 24V check on the horn, then move up to the column switch. (Need to replace an ABS sensor on my jeep first.. ARGH.. I just wanna work on the HMMWV.)

 

[Hummer Guy]

Was wondering if someone had a point to diagnosing what might be wrong with the horn on my M998.

I looked in the service manuals and didn't see any flow charts on checking the horn wiring.

So far, I've checked AT the horn. I've got 24V where I should. The other line has no voltage (or -). I tried to check it with someone pushing on the horn button and nothing changed.

Wondering what I should do next? I assume at this point either the horn switch isn't grounded property, the horn switch is bad, or the column connection is bad, or the wire from the column to the horn is bad.

You can just install an air horn; I could barely even hear the factory horn with the engine running

 

[papakb]

True, the stock horns suck! I originally thought about air horns but then where does the compressor go? I ended up with a 24v Federal Signal siren from a Navy police car that has an electronic air horn that will also rebroadcast the radio thru the speaker.

 

[mgFray]

The problem was the switch on the steering wheel. There is ground to the nut in the center, I connected the wire to that and horn went off.

Doing a voltage check between the "ground" side of the horn (with +24V connected), I got 22V. So that pretty much covers the resistance of the unit.

 

[Coug]

yup, stock horn just goes "meep meep". It's meant more for letting people walking nearby you are there, not yelling at other cars.

I wired a pair of Hella 24V horns into the circuit parallel to the stock horn.

https://www.amazon.com/HELLA-940800821-Black-Trumpet-Universal/dp/B01EG18Y8I

 

[mgFray]

I'm fine with the 'meep meep'. Just want everything to "work" like it should. I'm glad it's just the switch, and not the wiring.

 

[mgFray]

Ok, got a new button. Button now checks out electrically, but still doesn't work. After consulting the parts manual (for about the 5th time), TM-9-2320-280-24P-1 Figure 68. I just realized, the bushing (part 10) is missing. So even though the new button works, it isn't getting ground contact to actually work.

So _one more_ part to order.

 

[Mogman]

Same as the M151 so there should be plenty out there.

 

[Mullaney]

Ok, got a new button. Button now checks out electrically, but still doesn't work. After consulting the parts manual (for about the 5th time), TM-9-2320-280-24P-1 Figure 68. I just realized, the bushing (part 10) is missing. So even though the new button works, it isn't getting ground contact to actually work.

So _one more_ part to order.

.
Well that "bites" but at least you found the diagram in the TM.
Progress.
Slow but sure...