Testing the horn circuit

Bruce Wingate

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I've tracked down what I think are most of my electrical Gremlins, but my horn doesn't work. There is power to the orange wires going into the relay. (1984 K10 Silverado)

What I would like to do is test the circuits without taking the steering column apart because that is another set of problems for a different day

How can I test the relay and how can I trigger the horns from the relay socket?

I'll write up how I debugged the done light and radio circuits once I'm at a computer with a keyboard.

Thanks all
Bruce
 

SirRobyn0

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Ok a horn is a simple circuit. A relay has 4 terminals. One terminal is powered all the time, one terminal goes from the relay to the horn, one terminal gets power only when the horn button is pushed and one terminal is ground.

Take your test light remove the relay and check for power. You should have power on one terminal. Have an assistant push and hold the horn button, check again for power at the relay you should now see power at 2 terminals. Put the relay back in and check for power at the horn. If you have power at the horn the horn is bad. If you see two terminals at the relay with power when your friend presses on the horn button, but no power at the horn, most likely you have a bad relay. If you don't have power at two terminals when your friend is pushing on the horn then there is a problem further up stream. You can take the horn button off and check for power there.

Hopefully that all makes sense I've had quite a bit to drink tonight. So let me know if I need to clarify anything.
 

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It should be noted that the horn button completes the circuit on the ground side of the relay.
 

Bruce Wingate

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Thanks all.

Resolved the problem by working backwards. Tested each horn and they worked after cleaning the contacts and banging them a bit. Went to the relay socket and jumpered the orange power to green horn wire. Wiggled it and it started working. Sort of randomly applied power and ground to the relay itself and got it to trigger.

Now I've workedmy way back to the other end of the circuit and take the horn button off the (aftermarket) steering wheel. True to form for this truck, it was a half completed job with no horn contacts. Replacement stock components are in boxes waiting for that stage of the project.
 

WebMonkey

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good job.

same solution here.

my horn stated flaking out, then quit.

cleaned the terminal on the only horn mounted as well as the harness connector and that solved it.
 

nujac

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I had the same problem years ago the day I need to inspect my truck. Took the steering wheel apart and notice it was missing a ground. Do not know where the ground is located so I added a new one from the steering column mount bracket to the frame of the dash. Also solve the blinker not always working problem.
 

AuroraGirl

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I found that pressing the horn button(center pad of wheel) makes the horn activate

It’s an extensive test but it never fails to indicate whether or not there is a problem with the horn circuit
 

Crusader fixer

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Noted another in here related loss of ground to the steering column. How does this happen? I found an intermittent horn to be because it was getting a ground at the bottom of the column from the oil dipstick!
Now that was a surprise!
 

Raider L

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@Bruce Wingate,

Now, what did you do to get your dome light working? Wasn't that what you were printing?
I've had a problem with mine not working since the original dome light housing crumbled into dust, lens and all.
So I thought I'd be cool and put some after market one in. It worked fine but I changed my mind and wanted to put a original type back in and in testing the wires found that there was power in the orange wire and the white wire and I assume the housing provided the ground.
Well, it won't work but I have power up there but when I attach the wires it won't work . I must not have a good ground somewhere. I made sure when I was putting in the new carpet that the wiring was in good shape all the way up to the light. Also, there could be a problem in the switch to.
Power comes up there when I put the interior light on at the dash lights, and when the doors open from the courtesy lighting switch in the door jam.
 

mtnmankev

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Congrats of getting the horn working, very important item to have to deal with the idiots on the road.

I don't want to sound stupid, but I need to track down horn problems on both my squares, and having old man brain fade isn't helping any.
Can somebody please post a pic of the horn relay in it's natural position and habitat ?
My trucks are 82 and 84 vintage if that could affect the correct location.
Thanks in advance.
 

Bruce Wingate

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@Bruce Wingate,

Now, what did you do to get your dome light working? Wasn't that what you were printing?
I've had a problem with mine not working since the original dome light housing crumbled into dust, lens and all.
So I thought I'd be cool and put some after market one in. It worked fine but I changed my mind and wanted to put a original type back in and in testing the wires found that there was power in the orange wire and the white wire and I assume the housing provided the ground.
Well, it won't work but I have power up there but when I attach the wires it won't work . I must not have a good ground somewhere. I made sure when I was putting in the new carpet that the wiring was in good shape all the way up to the light. Also, there could be a problem in the switch to.
Power comes up there when I put the interior light on at the dash lights, and when the doors open from the courtesy lighting switch in the door jam.

I'm not positive the dome light works yet but I know the circuit is good. I got it working by tracking down a short. You are supposed to have power to the orange wire and the white is ground. The door switch completes the ground of the circuit (I'm explaining that wrong). The housing is plastic and I don't think it can provide a ground. If you have power in the white wire thats a problem but I don't know what it is.
 

Raider L

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@Bruce Wingate,

The housing is plastic but goes through a special process where it takes chrome plating and it is that, being metal that makes the ground through the housing. And strangely enough that White wire is power all the time because it is tied into the courtesy light under the heater duct down under the dash. Weird isn't it. The White wire comes from there and goes to the two pin switches in the door jam that when you open the doors, either one, the interior lights come on which is the dome light and the floor light. The ground for the dome light is the chrome plating on the dome light housing and the door jam switches ground is the hole in the metal where the switch is mounted.

The only reason why I know all that is because recently I was trying to mount a little light in my glove compartment. I knew that White wire was hot all the time so I tied the power wire to it for the light and put the ground wire soldered to a small piece of metal that touched a bare spot at the top of the frame around the glove box. Well, at night it worked fine but if you turned the interior lights on with the head light switch, the glove compartment light would not work. Figure that one out!

I discovered that the door jam wires were cut out of the circuit if the doors were shut and you turned the floor light on. And using the head light switch controls this. When you use the head light switch to turn the interior lights on, the floor light comes on and so does the dome light, but the head light switch doesn't need the door jam lights in the circuit so it cuts them out, both of them. And if you open the doors all the interior lights are already on anyway so it doesn't affect it. It's only when the doors are shut that I discovered all this weird wiring by close study of the schematic until I got it. If you look at your floor light, down by the heater vent next to the floor there are a bunch of Orange and White wires going to that light socket. There it is.
 

mtnmankev

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@Bruce Wingate,

The housing is plastic but goes through a special process where it takes chrome plating and it is that, being metal that makes the ground through the housing. And strangely enough that White wire is power all the time because it is tied into the courtesy light under the heater duct down under the dash. Weird isn't it. The White wire comes from there and goes to the two pin switches in the door jam that when you open the doors, either one, the interior lights come on which is the dome light and the floor light. The ground for the dome light is the chrome plating on the dome light housing and the door jam switches ground is the hole in the metal where the switch is mounted.

The only reason why I know all that is because recently I was trying to mount a little light in my glove compartment. I knew that White wire was hot all the time so I tied the power wire to it for the light and put the ground wire soldered to a small piece of metal that touched a bare spot at the top of the frame around the glove box. Well, at night it worked fine but if you turned the interior lights on with the head light switch, the glove compartment light would not work. Figure that one out!

I discovered that the door jam wires were cut out of the circuit if the doors were shut and you turned the floor light on. And using the head light switch controls this. When you use the head light switch to turn the interior lights on, the floor light comes on and so does the dome light, but the head light switch doesn't need the door jam lights in the circuit so it cuts them out, both of them. And if you open the doors all the interior lights are already on anyway so it doesn't affect it. It's only when the doors are shut that I discovered all this weird wiring by close study of the schematic until I got it. If you look at your floor light, down by the heater vent next to the floor there are a bunch of Orange and White wires going to that light socket. There it is.

My thanks to you, Raider L, for that detailed dissertation of educational knowledge.

Maybe now I will be able to fix my interior light gremlins.

Only been putting it off for two years now.
 

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