Horns have stopped working on my 75 and I'm trying to locate the horn relay. I've looked in my assembly manual but it doesn't show it very well.

 

From Peters '75 - it is under the left hand fender very visable as many wires attach there - to left of alternator. Could also be your horn button not hitting correctly. Mine only works when touched on upper left.

 

My 75 had a relay located by the fusebox which was defective and keeping the horn from working. I could hear it clicking when I pressed the horn button but no horn. 12volts directly to the horn itself showed that it worked. So I took the relay apart and the contacts were all burnt. Replaced it and the horn has worked fine since. FWIW.

Good Luck!

 

I stand corrected - the early '75's did have the relay above the fusebox per ACECO - per the Jan 1974 AIM page - but, my June 1975 has it under the left hand fender. I am learning all the time - FYI most AIM material was done in early 1974 and many changes were made to cars throughout the year - an example, my '75 has the vent hoses for Astro Ventilation but no AV - it was phased out towards the end of the model year. If you have time find out what month your car was mfg to determine early or late Vette. Peter

 

It's by the fuse box hanging with a three wire connector. One black, one green and one orange (from memory). If you ground the black one, the horns should blow. If you short the orange and green wires, that should bypass the relay and the horns should blow. If not, you don't have the 12 volts or the horns are bad or not grounded. My 78 had both horns bad. I bought an "A" and a "C" note at O'reilly's for about 10 bucks apiece. The relay is about 6 bucks. If you have a meter, you should have 12 volts on the orange wire all the time. The black wire runs over to the steering column and is grounded when you push the horn button. The green wire runs directly to the two horn hot connectors. The horns are grounded to the frame. If I'm wrong about the color of the orange wire, it's the one that's not green or black. I'm sure of those two. Make sure if you don't have 12 volts on the orange wire that you check the fuse. Again, it should always have 12 volts, even with the key off.
One additional note, the horn contact in the steering column could also be not grounding the black wire. To troubleshoot, ground the black wire on the relay, if the horns blow, the problem is in the horn contacts in the steering wheel. There is a small spring with a contact on the end that could be broken or missing. There is also a contact ***'y that is insulated and held on with three nylon pins that could be broken. Post back if you narrow it down and I can help if you need it.

 

I think its the other way around.The early would be under the hood and the late would be under the dash.(but I thought all 75s were under the dash)

 

Generally speaking the relay is next the the fuse panel. Mine was tucked up in with a bundle of wiring and I had to untangle it out to get to it. Relays are cheap, like $5-$8 at the parts store. Also check your upper horn contact. I pulled both horns, cleaned them up and tested them directly with 12v and they worked. Put them in the car and got nothing. So I changed the relay and got nothing. So I pulled the horn cap and found the arm on the upper contact that actually completes the circut, grounds the horn and thus makes it sound, was snapped off the upper contact because the previous owner didn't have any shims. So I needed a new contact and shim kit and now I have horn.

Not, as mentioned above, it is a little tempermental in terms of making contact. It works best if I push on the bottom half and 'pivot' the horn button rather than squarly in the middle of the button.

 

Not trying to hijack this thread... but I have a similar problem on my 81. The horn kinda works sometimes. Not sure if it's the horn, relay or just a bad connection. Where exactly is the horn located on an 81? since it just barely blows and my hearing ain't the best anymore, I can't seem to locate it. 'preciate the help.

 

Thanks to everyone for the input on the location of the horn relay for my 75'. It is under the dash near the fuse block and tucked up by the wiring harness. It has a green, black and red wire coming into the connector. I checked the red lead for voltage and found it to be live. I removed one horn and applied 12V and the horn worked. Next step will be to check horn button.

Pete

 

If you have 12 volts on the red wire, and you short it to the green wire (with or without relay in circuit) the horn should blow. If it doesn't, the problem is between the relay and the horn. The green wire goes directly to the two horns. In your pm to me, you said you shorted the black wire to ground with the relay out. That won't work. The black wire gives the ground to the relay to short the red and green wires internally. That's what happens when you press the horn button, it shorts the black wire to ground. If you manually short the red and green and they still don't blow, you need to work toward the horns. You may still have a problem in the steering wheel, but nothing will fix the horn until you get it to blow at the relay. Short the red and green together and check for 12 volts on the green wire at the horn. If it's not there, go back toward the relay and find the break. If it is there and the horn doesn't blow, the problem has to be the horn or the ground. If it blows when you short the red and green, but not when you ground the black wire (with relay in circuit) the relay is bad. If it does blow with the black wire grounded, but not with the horn button, the problem is in the steering wheel horn contacts. Make sure you're checking the horns that connect to the relay. The alarm horn if you have one, does not blow with the horn button or relay. The correct horns would be the horns between the headlights. Let me know. If you get stuck, pm me again and I'll give you a call and we can talk it over.