I need some help. My 1967 Corvette’s horns recently quit blowing and, of course, I found this out at a National Corvette Restorers Society (NCRS) event. Everything works great except the horns. When we returned from the event I went out to the garage and lo and behold the horns would blow, but only when I pushed the button hard in the 11 o’clock position.
My car is restored and I don’t have anyone in my area that I trust working on the car. I was hoping you could give me some troubleshooting tips to get me started.
Frank, I’m sure I can help you repair your Corvette’s horn problem. I am also going to take this opportunity to cover some other common Corvette horn problems as well as some troubleshooting tips.
Troubleshooting the Horn Circuit, Test the Horns
The first thing to always check is the fuse. I always probe each side of every fuse using a test light. On early Corvettes I always power or ground the test light from the battery. If the test light does not light on one side of the fuse you will find that the fuse is most likely blown.
If the test light does not light on either side of the fuse, you will need to look in the owner’s manual to see what that circuit feeds. Certain circuits will require that you activate something to power that particular fuse. Let’s check to see if the horns have failed internally. The horns on Corvettes are fed power by a dark-green 14-gauge wire connected from the horn relay.
Disconnect this green wire from the horns, hook one end of the test light to a ground and test for power at the green wire while someone is blowing the horn. This green wire’s insulation can become worn through where it passes from the horn relay through the radiator core support so be sure to check for any wire chafing in this area if the horns are not being supplied with battery voltage.
If there is power at the green wire when someone is blowing the horn you will need to check for a poor ground. Reattach the green wire and run a jumper wire from the battery ground to a paint-free spot on the horn body and try blowing the horn again. If the horn blows, remove the horns, clean the paint or corrosion from the attaching surface and reattach.
If you think the horns have failed internally with the ground jumper wire still in place, unplug the green power wire from the horn being tested and use a second jumper wire to supply 12V to the horns. If they don’t blow, the horns have failed internally and will need to be repaired or replaced.
Battery voltage is supplied usually by a red wire to the horn relay from the fuse box.
When the relay is closed, battery voltage is normally supplied to the horns through the green wire. The horn relay contacts can become corroded and may need to be cleaned. We will cover testing the horn relay and cleaning the horn relay contacts in part 2.
Horn Ground Circuit
Now for the ground circuit, normally this is where you will find the problem. When you push the horn button the ground is transferred through the black wire, allowing the horn relay to close and supply voltage to the horns.
This ground is supplied through the steering shaft. It travels up the lower section of the steering shaft, across the rag joint by a copper ground strap, back through the upper part of the steering shaft and up to the horn contact.
Check to make sure the copper ground strap at the rag joint has not been discarded or left off during a previous repair. These ground straps are composed of a thin copper strap or a copper mesh embedded in the rag joint.
If you think you may have a ground supply problem at the rag joint, or any point, you can run a jumper wire from a battery ground and touch the opposite end of the jumper wire to the potential problem, such as toward the firewall side of the steering shaft.
In part 2 we will finish this series by going over some other common horn ground circuit failures, checking the horn relay and their repairs. Vette