For you electrical gurus!

I can not get my horns to work on my '74.  The steering wheel contacts are working, and I can hear the relay pick up.  When the horn button is pressed, I get 12 volts at the horn connection.  Both horns work when connected directly to the battery. 
 
When the horns are connected to the car, I can hear the horns briefly "chirp" but they do nothing else. 
 
What's baffling is that I get 12 volts to the horn lead.  Is it possible that there is not enough current being delivered?  Bad horn relay perhaps?  I hope not... On the '74's, it is on the harness behind the dash, and I do NOT want to take that out again. 

Thanks in advance!

If you are getting a full 12v(or battery voltage) AT the horns, and the horns work if you shoot 12v to them, it does sound weird.
Couple o questions:
Are you checking voltage with a meter, or test light?
Did you test the horns on the car, or off?
If you checked voltage with a meter, but checked the horns off the car, I would suspect the horns are not grounding well....might try cleaning the bracket really well where the bolts go thru. However...you can show 12 on a meter, but once the horns activate, there is not enough amperage to power them up. This could be a bad relay, or a so-so connection anywhere in the circuit.
If you tested the horns ON the car(bolted up), and checked for voltage with a test light, I would suspect the relay, or a corroded connection somewhere in the circuit.

Thanks for the reply, Joel.

Tried the horns bolted in, and removed.  They are aftermarket horns with two terminals, and I ran one from each to the ground lug on the front bumper (vacuum tank) assembly.

Tried with the car on, and off, with a multi-meter.  Didn't try a test light, but that's a good idea as it may give me some indication of current flow.

Man, I really don't want to take that dash apart AGAIN!  The horn relay is buried in there; taped to the main harness between the speedo and tach if I remember correctly.

Have a good one.

Darryl

 
The horn relay on my '74 is in the harness to the left of the fuse box, just kinda hangin there. There is a buzzer in the harness between the tach and speedo, tho.
Hearing the relay "click" tells you that it has power, and is getting ground when you press the horn button, but it doesn't verify that the signal is actually getting to the horns. The contact points could be burnt, or gummy, and just not allowing a full voltage, full amperage signal AT the horns. If you can get a squeal, buzz, or other noise out of the horns, but not  a full blast, I would have to suspect either the relay is shot, or there is a ground or other connector problem. You might see a static 12v there, but under a load, the voltage may not be enough to blast them.

Thanks again!  I must be remembering the buzzer.  I'll have to get in there tomorrow and dig out the relay, I'd bet that's the problem. 

Darryl

I cant explain this but I had the exact same thing with my 72. The horns would make a slight grunt but not blow. I found a problem with the relay but dont remember how I arrived at that for the problem. The horn relay for mine was discontinued and I ended up using one for a 73. But once the relay was replaced my horn worked fine. I did the cleaning of the grounds for the horns. If I would run a solid 12 volt wire to the horns they would work. I'll have to see if I can find my troubleshooting paper work but it did lead me to the relay and that fixed my problem. The relay was only around 20 bucks from NAPA. Best of luck Rodney

Thanks Rodney.  I have a spare harness from a '75 that I've cannibalized, and I'm hoping the relay is on there.  I appreciate the response.

Darryl

Very possibly you have a bad ground to the horns try jumping a ground wire from the motor to the horn frame

I have the same issue with my 75 Corvette.  I at least have the dash out right now.  I tried jumping the red and green wire directly thinking it would at least honk.  It only grunts.  I just put a new relay on it so it might be bad as well.  I am just confused as to why it would grunt.  Did we ever figure out why it wasn't working?  I am getting 12 volts through my red wire.  Any new suggestions as I would like to get this thing fixed.  Also does the key relay it buzzes mine buzzes but was wondering if it had anything to do with the horn relay hanging down.  I love this old Vette.

Yep, it was the horn relay.  Very cheap, and as Joel pointed out, it was hanging on the harness near the fuse box and easy to swap out.