Why isn't my horn working...and where do I start ?

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diymirage

diymirage

HP@idle > hondaHP@redline
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If I unplug the green wire from the horn and put 12 volts to it, it honks

But, if I press the horn button on the steering wheel, nothing happens

Looking at it, I feel like I'm missing some parts (there are no springs in it)

And yes Rob, I took the horn button off, smarty-pants

20250410_152619.jpg
 
Run a jumper wire from that top wire to a known good ground. This will tell you if you a ground problem somewhere.
 
What year model? You know better, LOL. Horn relay. You can easily check by accessing the black wire out of the ignition connector out of the column, and grounding it. If not go to the relay. Some years are under the hood, some are under the dash
 
67Dart273 said:
What year model? You know better, LOL. Horn relay. You can easily check by accessing the black wire out of the ignition connector out of the column, and grounding it. If not go to the relay. Some years are under the hood, some are under the dash
Click to expand...
Come on now, I've been on here for nearly 2 decades and I've only had the 71 duster, y'all should know that by now

I'll check those 2 grounds and report back
 
diymirage said:
Come on now, I've been on here for nearly 2 decades and I've only had the 71 duster, y'all should know that by now

I'll check those 2 grounds and report back
Click to expand...
Nothing happens when i ground out the black wire on the steering wheel, i have not been able to get to the black wire coming out of the column (it looks like the way 4 wire trailer wires sit together, right ?


I did find this lil fellow, but i think its a buzzer of sorts, not a relay, so Ill have to do some more digging to find that

20250410_202059.jpg
 
The 71 Ply manual shows the horns, H2-16DGN/R (Dark GreeN/Red) goes to bulkhead cavity K. THAT MAY be a misprint, as they were wrong some years.

The horn button comes off the turn switch connector, not the ign sw connector. The turn connector is pointed on one end, the black horn wire is the one at the far, squared off end.

The horn relay is separate, has a 3 wire connector and a single, separate connector. That one is for the key in buzzer.

The 3 wire connector has small black--horn button, violet--from battery HOT, and dark green / red is back to the horns.

See if you have power on the violet, and jumper the black wire terminal to ground, should sound the horns, or at least "click" the relay
 

67Dart273 said:
The 71 Ply manual shows the horns, H2-16DGN/R (Dark GreeN/Red) goes to bulkhead cavity K. THAT MAY be a misprint, as they were wrong some years.

The horn button comes off the turn switch connector, not the ign sw connector. The turn connector is pointed on one end, the black horn wire is the one at the far, squared off end.

The horn relay is separate, has a 3 wire connector and a single, separate connector. That one is for the key in buzzer.

The 3 wire connector has small black--horn button, violet--from battery HOT, and dark green / red is back to the horns.

See if you have power on the violet, and jumper the black wire terminal to ground, should sound the horns, or at least "click" the relay
Click to expand...
Thanks, Ill see if i got a minute to try this tomorrow and report back
 
67Dart273 said:
The 71 Ply manual shows the horns, H2-16DGN/R (Dark GreeN/Red) goes to bulkhead cavity K. THAT MAY be a misprint, as they were wrong some years.

The horn button comes off the turn switch connector, not the ign sw connector. The turn connector is pointed on one end, the black horn wire is the one at the far, squared off end.

The horn relay is separate, has a 3 wire connector and a single, separate connector. That one is for the key in buzzer.

The 3 wire connector has small black--horn button, violet--from battery HOT, and dark green / red is back to the horns.

See if you have power on the violet, and jumper the black wire terminal to ground, should sound the horns, or at least "click" the relay
Click to expand...
so the picture i posted looks to be a "horn relay/buzzer"

there was a wire on the bottom post, long gong, but if i ground that out it will buzz incessantly

on top there is 3 wire tab, purple, green/red tracer and black/white tracer

there is power to the purple wire

i tried grounding out the black/white post and nothing happened

however, when i jumped the purple to the green/red the horn sounded


so am i right to assume the signal wire from the horn button, or the relay is the issue?
and could i replace this with a "modern" (read, 5 dollar) relay?

here is a listing for the relay think i have, and well, for that kinda money, ill keep dropping it in neutral and revving it

Horn relay and ''key-in-ignition'' buzzer for all 1971-73 Plymouth Duster - Valiant - Scamp and all 1971-73 Dodge Dart - Demon - Sport
 
Id test light it at the horn first that easiest and you can sort of look through the hood and see if the light is lighting however Grant horn switches always are a pita for some reason...I could tell ya a story about a Grant horn switch but i wont ...I wont.... :lol:
 
Dartswinger70 said:
Id test light it at the horn first that easiest and you can sort of look through the hood and see if the light is lighting however Grant horn switches always are a pita for some reason...I could tell ya a story about a Grant horn switch but i wont ...I wont.... :lol:
Click to expand...
I will give this a try, but at this point I already know the hot wire leading into the relay and the feed leading out of the relay are good

That just leaves the relay and the signal wire from the horn (which is a ground ?)
 
diymirage said:
I will give this a try, but at this point I already know the hot wire leading into the relay and the feed leading out of the relay are good

That just leaves the relay and the signal wire from the horn (which is a ground ?)
Click to expand...
No should be hot, the horn grounds through bolting to the body OR there is a ground wire from the horn to the body. If it is a wire it will be a short wire from the horn to a bolt on the rad support etc. Im saying if cause i do seem to remember a short ground wire to the horn...I havent looked for a while. Basic diagram here post 10...so the horn button is energizing the relay that then sends the hot side through to the grounded horn so like I was saying if you hook test light to ground take wire off at horn and probe, push horn button inside car and it lights you either need a ground or its a dead horn if it doesn't light then you have an issue with your hot side of the signal thats tracing back from the horn to the relay to the switch etc.

Issue with horn
 
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i have mine wired directly up to the battery threw a cheap switch rated for 70 amps i got at auto zone. i would start by checking the relay and the horn, use a jumper wire to test the horn directly from the battery, if the horn no make noise then you know its the horn that's bad.
 
Dartswinger70 said:
No should be hot, the horn grounds through bolting to the body OR there is a ground wire from the horn to the body. If it is a wire it will be a short wire from the horn to a bolt on the rad support etc. Im saying if cause i do seem to remember a short ground wire to the horn...I havent looked for a while. Basic diagram here post 10...so the horn button is energizing the relay that then sends the hot side through to the grounded horn so like I was saying if you hook test light to ground take wire off at horn and probe, push horn button inside car and it lights you either need a ground or its a dead horn if it doesn't light then you have an issue with your hot side of the signal thats tracing back from the horn to the relay to the switch etc.

Issue with horn
Click to expand...
Ok, the black wire on the steering wheel does not have any power going to it, so that must be the most likely culprit

I took the wheel off and there is no power to the black wire with the wheel on it, so I will have to trace that one back

As far as the diagram, it looks like my relay only has 3 wire for the horn, plus one for the buzzer

No wire for a keyed source going to the horn

20250411_150637.jpg
 
diymirage said:
Ok, the black wire on the steering wheel does not have any power going to it, so that must be the most likely culprit

I took the wheel off and there is no power to the black wire with the wheel on it, so I will have to trace that one back

As far as the diagram, it looks like my relay only has 3 wire for the horn, plus one for the buzzer

No wire for a keyed source going to the horn
Click to expand...
basic horn operation.

to power the horn
  1. constant on power source to the horn relay (Older cars its mounted under the hood and is tapped off the alt wiring.) your car I'm not sure where it gets its constant feed from
  2. from the switched side of the horn relay power goes to the horns then through the horn mechanism and to ground.
to switch the relay on and off
  1. The other post (of the 3 for the horn relay) runs to the steering column then to the horn switch
  2. the horn switch grounds out the wire causing the relay to energize.

The colors ARE NOT representative of your cars wiring just representing 12V and grounding (note BLACK and GREEN are not Ground on our cars

1744404798591.png


your car has the buzzer and relay in one and under the dash so the pinout of the relay buzzer is different but this is how it all works



Your 71 from the FSM

operation:

Horn

"+12V" always on from the battery OR main splice etc.
"Horn Switch" when you press on the horn switch it closes the NO (Normally Open) contact and makes a path to ground.
"To Horn Switch" gets the ground from the "Horn Switch" so the coil will energies and close the NO "To Horns" contact
"To Horns" now provides 12V to make the horns sound

Key-in Buzzer
"+12V" always on from the battery OR main splice etc.
IF the key is in the ignition the NO "Key Switch" passes the ground to the NC (Normally Closed) contact in the relay
This provides a ground to energies the coil in the relay.
The coil will energies and close the NO "To Horns" contact
The "To Horns" NO contact now provides 12V to make the horns sound
BUT at the same time the "To Horns" NO contact closes the NC contact in the relay opens and the horn makes one beep rather than stay on continuously


1744407310764.png

H3-20BK* (black from horn switch, grounding energizes the horn relay)
H2-16DGN/R* (dark green with red trace, provides 12V to the horns when the horn switch is pressed and the horn relay is energized)
H1-16 V (violet, constant on 12v (might go through a fuse?)
M16-20BK (black, makes a ground if the key is in the ignition and the door is opened)


1744407622069.png



1744405592478.png




MYMOPAR.COM download free your cars factory service manual and or the wiring diagrams available. and start tracing things. YOU MUST know this stuff if you are going to work on your classic car.

CLASSICCARWIRING.COM great source for laminated full color diagrams (best $25.00 I ever spent)
 
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Dana67Dart said:
basic horn operation.

to power the horn
  1. constant on power source to the horn relay (Older cars its mounted under the hood and is tapped off the alt wiring.) your car I'm not sure where it gets its constant feed from
  2. from the switched side of the horn relay power goes to the horns then through the horn mechanism and to ground.
to switch the relay on and off
  1. The other post (of the 3 for the horn relay) runs to the steering column then to the horn switch
  2. the horn switch grounds out the wire causing the relay to energize.


Your 71 from the FSM

operation:

Horn

"+12V" always on from the battery OR main splice etc.
"Horn Switch" when you press on the horn switch it closes the NO (Normally Open) contact and makes a path to ground.
"To Horn Switch" gets the ground from the "Horn Switch" so the coil will energies and close the NO "To Horns" contact
"To Horns" now provides 12V to make the horns sound
Click to expand...
The part I don't get is where it says "to horn switch gets ground from the horn switch"

Does this mean the horn switch completes a grounding circuit, instead of sending a positive current to the relay ?
 
diymirage said:
Does this mean the horn switch completes a grounding circuit, instead of sending a positive current to the relay ?
Click to expand...
correct.

and if your column is not properly grounded... no horns

This is at least in 67.... Here is another wiggle. Since the steering shaft makes the final ground path, the steering shaft must be grounded and it is 2 pieces with plastic between so they added a clip that electrically connects the upper 1/2 to the lower 1/2. There is a TSB about using a screw or sometining like that to replace the clip should it fail. My guess is they made a modification to later years to no have this issue.

1744409597542.png
 
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Dana67Dart said:
correct.

and if your column is not properly grounded... no horns

Here is another wiggle. Since the steering shaft makes the final ground path, the steering shaft must be grounded and it is 2 pieces with plastic between so they added a clip that electrically connects the upper 1/2 to the lower 1/2. There is a TSB about using a screw or sometining like that to replace the clip should it fail. My guess is they made a modification to later years to no have this issue.

View attachment 1716391479
Click to expand...
So to check the relay, I should ground the "from switch" post ?

How interesting, I expected it to be a 12 volt signal, like when you want to turn light on


I'll check that grounding path when I get a minute
 
diymirage said:
so the picture i posted looks to be a "horn relay/buzzer"

there was a wire on the bottom post, long gong, but if i ground that out it will buzz incessantly

on top there is 3 wire tab, purple, green/red tracer and black/white tracer

there is power to the purple wire

i tried grounding out the black/white post and nothing happened

however, when i jumped the purple to the green/red the horn sounded


so am i right to assume the signal wire from the horn button, or the relay is the issue?
and could i replace this with a "modern" (read, 5 dollar) relay?

here is a listing for the relay think i have, and well, for that kinda money, ill keep dropping it in neutral and revving it

Horn relay and ''key-in-ignition'' buzzer for all 1971-73 Plymouth Duster - Valiant - Scamp and all 1971-73 Dodge Dart - Demon - Sport
Click to expand...

EDIT........I thought you had grounded the black to test
Sounds to me like relay is bad
 
67Dart273 said:
EDIT........I thought you had grounded the black to test
Sounds to me like relay is bad
Click to expand...
Correct, I did try that, but just to be sure I tried it again

Nothing happens when I ground out that post (or put power to it, for that matter)

So a new relay is in order
 
You did confirm that the black wire has continuity between the horn relay and the steering wheel, right?

– Eric
 
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