To find the correct wire, you'll need to:
1. Consult a wiring diagram: A factory service manual for your specific year and model Caprice Classic is your best bet. These diagrams show the exact color codes and routing. You can often find these manuals online (though they can be costly) or at auto parts stores (sometimes on microfilm).
2. Trace the wires: Start at the horn button itself and carefully trace the wire(s) leading away from it. Be cautious not to damage any wiring. Follow them to where they connect to the horn relay. This is a more hands-on approach but allows you to visually identify the wire.
3. Use a test light or multimeter: With the ignition on, carefully probe the wires at the horn button with a test light while pushing the horn. The wire that shows power when the horn is pressed is likely the one going to the relay. A multimeter is even better as you can check continuity directly.
Without a wiring diagram specific to your vehicle, relying on color alone is unreliable. The safest and most accurate way to determine the correct wire is by using a combination of the methods above.
