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Discussion Starter #1
I thought I had this solved but the gremlins came back to haunt me. O.K. Here goes... Bought a 70 Chevelle that had an old Grant steering wheel in it. The horn was not working so I put in a new horn relay, still didn't work. Found I had twelve volts at the horn plug so I bought a generic horn from a chain store and eeeverything was fine. Then I changed the old Grant wheel to a new one. The horn worked O.K. but I noticed that if I hit the outer part of the steering wheel with my hand fairly hard the horn would blow. Now about a week later the horn doesn't blow at all and the horn relay makes a funny thumping kind of sound when I press the horn button. After trying to figure out what was going on for about an hour or so I'm going in for the night and shut the hood of the car and the horn relay starts making a buzzing sound and thumping like someone is pressing the horn button. The wiring on this car has been hacked by other people, wires cut and reconnected etc. etc. so it is difficult to know what's going where. ANyone have any insight would be appreiciated. I just read Desert Sun's post and Bob M's excellent response about grounding steering shafts but I don't know if that applies to my 70 or not.
 

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The wire coming from the horn relay which connects to the plunger button on the steering wheel horn assembly is there to transfer a ground connection back to the horn relay coil. The ground has to come from the steering wheel which gets it's ground from the steering box and it is transfered through the steering coupling via a ground strap on the coupling. I would check to see if your steering wheel has a good ground. It's a very simple circuit. Also make sure your horns are making good connection to the body of the car. They get their ground from the mounting point on the car.
 

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Discussion Starter #3
O.K. I'll check for that strap on the steering coupling again, I looked at it last night and I don't see any strap or wire at all around the steering coupling at the steering box. Question: The horn relay has two screw connections and three plug connections. There are three heavy (battery?) wires on the "bat" screw connector and nothing on the other screw connector. What's that other screw connector for? There is one plug connector wire going to the horns, another plug connector wire going to I think the backside of the fuse box and the third plug connector goes down with a bunch of other wires along the bottom of the radiator support to somewhere. Does that part sound right? I'm suspitious about the screw terminal on the horn relay with no wire on it.

Thanks
 

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The way most horn relays are wired are as follows!

The horn relay serves as a power junction also. The heavy red wire from the battery goes to the horn relay. If you have an ampere gauge there will usually be a smaller black wire connected with the heavy red wire on the relays battery terminal. The other heavy red wire typically is just the supply wire going to the fuse panel at the firewall. There should be two other wires connected to the relay. One will be a dark green wire which supplies switched +12 volts to the horns, the other wire goes to the horn assembly on the steering wheel. This wire supplies a ground for the relays coil to pull-in. Hope this helps. M22
 
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