Vette(s): 1990 C4 coupe, Bright Red, L98, auto (stock)
According to my 1992 service manual (most C4s are similar) the horn fuse is located on the right hand end of the dash near the passenger's door. The fuse you are looking for is a 15-amp fuse labeled THEFT. The steering wheel horn buttons activate a horn relay located below the right side of the dash just above the bottom cover (knee bolster) near and below the back of the fuse cluster. This relay simply closes the circuit between the fuse and the horns. The relay is also triggered by the Central Control Module for use by the Security System, but that probably won't be a factor in your problem. The wire color between the fuse and the relay input is orange. The wires from the relay to the horns are dark- green color, and go through just one connector C100 located in the left hand side of the bulkhead connector into the left engine compartment. Finally the wire from the horn buttons to the relay are black and pass through the C204 connector located on the right side of the steering column.
Check the fuse first. Then activate the horn button and listen for a clicking sound from the bottom of the right side of the dash. If that clicks then the problem is between the relay and the horns, probably at the bulkhead connector. If there are no clicks the problem is most likely the relay itself or the orange wire connection to the fuse. That's about all there is to it. As a C4 owner I know that NOTHING in the dash is easy to fix. However the factory service manual is absolutely essential in doing any repairs of a C4 Corvette. I hope this is the help you need.
I'm quite sure the horn circuit in your '87 is the same as the circuit in my '84. The fuse for the horn is the CTSY/CLK fuse. If that's bad, you would loose a lot of other things, too! The horn relay is behind the center panel in your dash.
I have replaced the steering wheel in my '84 with a '87 wheel, so I've tried both the '87 and the '84 horn buttons in my "new" wheel. The '84 button fits my '87 wheel just fine, and in fact, I prefer the '84 button over the '87. I'm going to guess that you have rust in your contacts inside your horn button. The button comes off with a little prying around the edge. There is a wire from the horn button to the slip ring contact that removes by pushing down on the sleeve and twisting the sleeve CCW (like removing a light bulb). Caution: The sleeve is delicate. If you ground that wire your horn should honk.
7/7/17 Correction: Brain fade! The steering wheel I installed on my '84 about 12 years ago was from an '86, not an '87. My suggestions may be all wrong, but hopefully will be similar.
Vette(s): 1985 Coupe-L98/Auto,Bright Red/Carmine.
1974 Coupe-L48/4speed, Medium Red Metallic/Black Deluxe.
Listen for the horn relay to click when you press on the horn button. No click could be no contact on the button, bad fuse, or bad relay. If you do hear a click, then the fuse, and button contacts are good, and you would go for the relay at that point. Just because the relay clicks does not mean it is making contact on the horn circuit(from relay to horn(s))
____________________________________ Joel Adams My Link
Vette(s): 1976 CorvettE , 1984 Corvette changed to a carb aluminum heads....., Z51 suspension and fully outfitted with Vette brake products upgrades
The relay that operates your rear hatch is the same relay for your horn so you can swap them out to do a quick test if you don't hear it click for the horn test both of them in the hatch it could be a wiring issue like what was on my 84
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