* Large Gauge Wire (B+): This is the main power output wire, and it connects directly to the battery's positive terminal (often via a heavy-gauge cable running to the starter solenoid).
* Smaller Gauge Wire (Ignition): This wire provides the alternator with the signal voltage it needs to begin charging. This wire is connected to a switched ignition source; it only gets power when the ignition is turned on. This is NOT connected to the starter. You'll find this wire connected to the ignition harness, often near the fuse box or ignition switch itself. Look for a smaller gauge wire going to a connector that gets power only with the key on.
* Smaller Gauge Wire (Sense or "S"): This wire is a sensing wire. It's connected to a point on the vehicle's wiring that provides a voltage reading directly from the battery. This allows the alternator to accurately regulate its output voltage regardless of voltage drops in the main charging cable. This wire is usually attached to a smaller gauge wire going to a point near the battery, often on the same terminal as the battery voltage gauge. It may sometimes be a small spade connector on a part of the harness near the battery.
Finding the wires: You'll need to trace these smaller wires from the alternator connector back through the engine bay harness. It will be challenging if the original harness has been heavily modified. Look for wire colors consistent with the alternator wiring diagram, which might be found in a 1977 Chevy 350 repair manual or online. Remember that wire colors can vary slightly depending on factory options or modifications.
