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Old owner screwed up turn signal so replaced also new relay and new horns.
Now horn blows constantly so I disconnected the green wire from relay. Now if I push horn button the relay clicks like I think it should, So I assume that end is ok so the circuit must have a ground somewhere?? I am stumped Any help is appreciated THANKS
Just because the relay clicks doesn't mean it isn't shorted inside. You don't say what car you have, but I just replaced the relay on my '78 Toro to get the horns working. Very easy to do, about $20 for the relay, and the horns work fine now.
I don't understand how an unintended ground somewhere could cause the horns to blow constantly. The green wire feeds power to the horns, and the horns are grounded through the horns themselves. So they already are grounded. The only way the horns can blow constantly is if the green wire is constantly getting 12 volts, not just when the horn button is pressed. The only way that can happen is if the relay is feeding it power all the time, instead of just when the button is pressed, and that can only happen if it's shorted inside.
Also, the horn relay typically has other wires connected to it, including power directly from the battery as the horns work all the time, even with the ignition off. You want to make sure all of the wires that meet at and connect to the relay are connected to the proper lugs and nothing is shorting to the green wire.
Last edited by jaunty75; November 12th, 2017 at 09:46 PM.
Ok so Now I assume there is a short inside the column is there a way to test for that ?? Oh its a 70 442 with sport wheel ?? The connections to relay look good so I guess I go in the column kinda of a pain
If the relay works with the horn button there is no short of problem between the 2. Check to see if the voltage switches on and off when you depress the horn button.
Check to see if the voltage switches on and off when you depress the horn button.
He says the horns blow constantly. I think the only thing he'll find here is that there is a constant 12 volts coming off the relay, and we already know this to be true because the horns blow constantly.
Yes, if the relay clicks, I would assume it's working, at least mechanically. Pushing the horn button energizes an electromagnet (the thing with the wire coiled around it in Figure 12-99 below) which closes the switch in the relay causing the horns to blow. Releasing the horn button de-energizes the magnet, the switch opens, and the horns stop blowing.
But it seems that the switch in your relay is closed electrically all the time, not just when the magnet is energized (horn button pressed). That's why I suggest a new one.
Rockauto has them for a '70 442 for $50. That's fairly expensive, and you might not want to spend that much money until you know for 100% sure the relay is bad.
Do you have a 1970 Chassis Service Manual? The horn system is covered on pages 12-47 to 12-49, with the horn relay troubleshooting procedure on page 12-49. I've copied and pasted the relevant pages below.
Here's what the relay looks like up close. The threaded stud is terminal 1 in Figure 12-99. It's where the wire from the battery attaches. There are usually multiple wires attached at this point. On my car there are four. Terminal 2 is where the black wire attaches. It is the wire from the horn switch on the steering wheel. Terminal 3 is where the thicker green wire to the horns attaches. It should have a connector with an ear on it that will allow it to fit onto lug #3. Terminal 4 is for the key buzzer, and the wire that attaches there, at least on my car, is red with a black stripe.
Here's a photo of the wired-up relay on my car. The red-with-black-stripe wire is toward the bottom and can't be seen.
All the more reason to check it before buying another one. Unless the wires are not connected correctly to the relay, which is kind of hard to do, I don't see what the problem could be other than a bad relay, especially given that you do hear the relay clicking when you press the horn button.
November 12th, 2017, 04:42 PM
Horn issues
