Please Help! Horn Doesn't Work!!

DoggyDiesel

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Hello.
I am new here so sorry if I get something wrong... I'll try and keep it short and sweet including as many details as possible.
This past April I bought an 84 GMC K25. It has a 6.2 diesel, sm465 trans, np208 transfer case, and 4:10 gears. I bought it non-running, sitting in a literal swamp, and drug it home.
When I got into it, the fuel tank was half full of 10 year old diesel, the injection pump (IP) turned out to be shot, and there was an electrical mess throughout the truck that could have been put together by a caveman.
I replaced the fuel tank, changed the IP, took out all the necessary wiring, and, in 4 months time had it running.
Here's where the problem(s) come into play.

1. I got a new grill for the front, and before I put it together I wanted to make sure the horn worked. It didn't. So I went around, cleaned the horn grounds up and nothing. So I figured it could be the relay. Messed around with that for a while and got the relay to click and buzz sporadically. I then took the top of the steering wheel apart and took the cup and spring out (with the steering wheel on) and cleaned all the rust up that was in there. This was all to no avail. I took the fuse panel apart, looked and cleaned contacts on both sides of the firewall, and still NOTHING...

2. Today as I was working on this issue, I did notice one thing - the dome lights (one by the shifter and one in the roof of the cab) come on whenever I press the horn. I would assume this is a grounding issue?

3. One more quick issue if you are feeling up to it. ;) Whenever the light switch gets pulled the blinker indicators both come on in the dash. The blinkers/flashers are then unoperational. I do have the rear harness cut currently. If it does not have a complete circuit to run could that cause this problem?

Any help is appreciated. I'm just trying to get the truck running under legal parameters!:laughing1:

Thanks Again!
 

Turbo4whl

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Several issues for sure. The horn relay is hot all the time. The button on the steering wheel completes the ground for the relay. The relay when triggered sends current to the horns. The dome circuit is also looking for a ground. Through the door buttons or the headlight switch. The first thing to check is all the ground leads that bolt to the cab metal above the parking brake.

If the instrument panel looses it's ground, the turn indicators will light up with the parking lights on. This is also one of the ground wires above the parking brake.

Check this and post what you find.

Welcome to the forum.
 

DoggyDiesel

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Thanks for the input. It's really appreciated.
I went investigating this evening and checked on the condition of the door buttons, to which I found them both stuck in and all rusted. I pulled the driver's side one out and there was no wire or anything attached to it. I will be going fishing in the kick panel now with wire to try and retrieve that. The passenger's side went a lot smoother, but it was very rusty.
So, I will order a couple of them tomorrow, or in the near future.

On the ground side of things, I haven't had a chance to take them off and clean them up by the parking brake, but glancing at them it appears the components under the dash are quite rusty.
I will clean that up and hopefully that is the culprit.
 

WP29P4A

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We had the same horn problem on my son's truck, I traced it down to the connectors where the wire connects to the horns. I cut off the connectors and replaced them, worked great after. Connectors didn't look that bad, but they didn't work before replacing. Might want to test the horns with a jumper wire off the battery before spending too much time on wiring.
 

Rusty Nail

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Did you check operation of the horn seperate from the truck? A 9v battery will make it work...:shrug:
Reckon it's pretty tough to make a bad horn honk, just sayin. :)
But dont you got two? Neither one works orrr???
 

squarelyfe

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Run wires direct from the battery to the horn to make sure it works first. Doesn't hurt to take some sandpaper to the contacts and clean them up.

I had a recent issue where the horn contact in the steering column had a weak or pushed in contact spring. The horn contact cam would not touch it because it fell back far enough. If you push the horn button can you hear the relay making noise? If not, it may be in the turn switch. That peg in the photo is spring loaded. The spring could have lost tension from getting hot on a short or just worn. When it happens the cam won't touch the peg. You can also remove the horn button and take a screwdriver to the contact and then the center shaft at the same time and you should hear the relay it's as if you were pushing the horn button.
 

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