Crazy horn problem

[j.d.]

73 road runner, all new wiring harneses from m&h. Horn beeps just fine until you start the engine then it begins to chatter. Seems to be trying to put power to ground when you push the horn button as you can feel it on the shifter handle. Searched an searched. Any suggestions of what it could be. Maybe ignition switch. Need help

 

[BeepBeepRR]

Could it be a chattering horn relay?

 

[j.d.]

Could it be a chattering horn relay?

Nope , changed that. Thanks

 

[yella71]

make sure they are grounded good

 

[j.d.]

make sure they are grounded good

Yep, grounds are solid. Thank you

 

[Builderguy]

I would have to know the voltage going to the horn, without the car running, and with the car running. Then need the voltage at the horn when the horn button is pressed and when it is "not pressed". Also need to know the voltage at the battery both in the running and non running condition. May be that the horn is failing and the increased voltage while running is enough to cause the chatter issue. May also be that the horn is fine and the charging system has an issued that is causing the chatter. My first though would also have been the Horn Relay or the ground.

 

[j.d.]

I would have to know the voltage going to the horn, without the car running, and with the car running. Then need the voltage at the horn when the horn button is pressed and when it is "not pressed". Also need to know the voltage at the battery both in the running and non running condition. May be that the horn is failing and the increased voltage while running is enough to cause the chatter issue. May also be that the horn is fine and the charging system has an issued that is causing the chatter. My first though would also have been the Horn Relay or the ground.

Hi builder, here it is.voltage to horn not running 0. Voltage to horn running .012. Voltage at horn while running with horn button pressed is jumping all over the place maybe between 1 to 3 volts or so just like the horn chatter. Voltage when horn button is not pressed with engine running is .023. Voltage at battery engine running is 15.08. Battery voltage not running is 12.84. Also unhooked all alternator wires an no changes. This things driving me crazy. Let me know what you think. Thank you in advance jd.

 

[Builderguy]

Hmmmm,
You need to isolate where the issue is. Best place to do this is at the relay. Problem is I can't remember if that relay is a 4 wire or 3 wire. I don't have access to my books right now and can't get a good answer from the net as the free service manuals stop at 1972.

I think it is a 3 wire at the relay so it should work like this: One wire goes to the horn. I think it was green or dark green with a red stripe but I am going from memory. Locate that wire and unplug the harness from the relay and apply 12V to this wire, the horn should beep. If so this wire is good.

Second wire goes to the horn switch on the steering wheel. If you leave the harness intact, but back stab that wire with a safety pin and then connect that that back stabbed pin to ground, the relay should close and horn should activate. If the horn works the this means that the wire from here (the relay), to the horn pad, thru the firewall is broken somewhere.

If it doesn't close the relay, the relay is either bad, or you have a power issue.

Third wire should have 12V constant power.

 

[j.d.]

Hmmmm,
You need to isolate where the issue is. Best place to do this is at the relay. Problem is I can't remember if that relay is a 4 wire or 3 wire. I don't have access to my books right now and can't get a good answer from the net as the free service manuals stop at 1972.

I think it is a 3 wire at the relay so it should work like this: One wire goes to the horn. I think it was green or dark green with a red stripe but I am going from memory. Locate that wire and unplug the harness from the relay and apply 12V to this wire, the horn should beep. If so this wire is good.

Second wire goes to the horn switch on the steering wheel. If you leave the harness intact, but back stab that wire with a safety pin and then connect that that back stabbed pin to ground, the relay should close and horn should activate. If the horn works the this means that the wire from here (the relay), to the horn pad, thru the firewall is broken somewhere.

If it doesn't close the relay, the relay is either bad, or you have a power issue.

Third wire should have 12V constant power.

Hi builder, it is a 4 wire relay. Does that make a difference?

 

[Nacho-RT74]

71/73 relays are 4 prongs relay but one of them is for the key in buzzer function. The other three prongs grouped together are the horn relay function itself... Positive on violet wire, Trigger ( ground coming from horn switch ) on black wire and output to horns ( positive ) on green with red tracer wire.

74s are 3 prongs, because key in buzzer was set in another system

 

[Builderguy]

Yup, thanks Nacho. My memory is slowly slipping.
The single spade from the fuse box is constant 12V (violet wire)
The one going to the horn switch (horn button) Black wire is the one you back stab and ground while the harness is still on the relay. The horn should work doing this and you should hear/feel the relay. If the horn does not work and you don't hear/feel the relay, it is probably a bad relay. I know you changed that but that doesn't always mean it is good.
The one going to feed the horn is, the one feeding the horn. LOL If you unplug the harness and put 12 V to the wire that is green with red tracer, the horn should work.
This should tell you where your problem lies.

 

[j.d.]

Yup, thanks Nacho. My memory is slowly slipping.
The single spade from the fuse box is constant 12V (violet wire)
The one going to the horn switch (horn button) Black wire is the one you back stab and ground while the harness is still on the relay. The horn should work doing this and you should hear/feel the relay. If the horn does not work and you don't hear/feel the relay, it is probably a bad relay. I know you changed that but that doesn't always mean it is good.
The one going to feed the horn is, the one feeding the horn. LOL If you unplug the harness and put 12 V to the wire that is green with red tracer, the horn should work.
This should tell you where your problem lies.

Thanks you guys. Not solved yet. Got to get back in there and search.

 

[kiwigtx]

Either a loose connection inside the horn switch under your steering wheel....or a bad track on the contact ring for the horn switch.

Sounds like engine vibrations are travelling up the steering column and making this problem occur.

Relays do not normally chatter.

 

[Builderguy]

As kiwigt stated, could be the horn switch itself.

I don't recall what keeps the contacts apart (spring, plastic, or something else), regardless; if it grounds (from engine vibration or some other action) and the wiring is intact, the horn will sound. All that is needed to ring is a path to ground. If the switch is bouncing around internally, that could be your problem. If I recall there are tiny springs keeping the contacts apart.

 

[j.d.]

Either a loose connection inside the horn switch under your steering wheel....or a bad track on the contact ring for the horn switch.

Sounds like engine vibrations are travelling up the steering column and making this problem occur.

Relays do not normally chatter.

I’m thinking you have something there. I did in fact removed the rag joint which would increase the vibration. Also there is some wear on the contact ring. Can these rings be replaced? Thank you for your input. Will work with that and see.

 

[kiwigtx]

As kiwigt stated, could be the horn switch itself.

View attachment 1019463

I don't recall what keeps the contacts apart (spring, plastic, or something else), regardless; if it grounds (from engine vibration or some other action) and the wiring is intact, the horn will sound. All that is needed to ring is a path to ground. If the switch is bouncing around internally, that could be your problem. If I recall there are tiny springs keeping the contacts apart.

Very small insulators inside that type of switch and equally small springs holding the contacts apart.

 

[dadsbee]

Is your ground jumper in place...

 

[j.d.]

Is your ground jumper in place...
View attachment 1019606

Yes,ground wire is in place. Thanks

 

[Nacho-RT74]

Either a loose connection inside the horn switch under your steering wheel....or a bad track on the contact ring for the horn switch.

Sounds like engine vibrations are travelling up the steering column and making this problem occur.

Relays do not normally chatter.

or broken turning switch at the contact stud, grounding elsewhere around

also wire peeled off accidentally reassembling the column and having exposed the strands

Ring can be replaced, yes ( if you find it ), but that wouldn't make chatter the horn. It can make contact or not, but that doesn't make to work the horn, just the switch or an accidental grounding around. The ring function is make able the contact on a rotation movement instead a wire turning around, but not close the circuit like the switch is

 

[j.d.]

Either a loose connection inside the horn switch under your steering wheel....or a bad track on the contact ring for the horn switch.

Sounds like engine vibrations are travelling up the steering column and making this problem occur.

Relays do not normally chatter.

well i believe your right. took the steering wheel and extension off then grounded the contact wheel that rides on the contact ring with the engine running and the horn works. hurray. the column does have vibration. now what to do about. thank you fellas so much for all your imput. jd