The large red wire that leads...
The large red wire that leads to the positive post on the battery to the output terminal on the alternator is the only connection necessary for a one-wire alternator. By removing this black plug, most one-wire Powermaster alternators can be converted to three-wire installations, which is preferred if you have a choice.
What's All This Fuss About One-Wire Alternators?
The Powermaster people tell us that the most asked tech question is: "How do I hook up a one-wire alternator?" One-wire alternators are becoming increasingly popular in modified cars as well as typical street cars due to their simplicity. The only wire that needs to be connected is a cable from the large output terminal on the alternator to the battery. One-wire alternators begin charging using a circuit that senses internal voltage once the alternator is spinning fast enough. This is why one-wire alternators require the engine to be revved past roughly 1,500 rpm to begin charging. Once energized, one-wire alternators will charge at idle no problem. Factory three-wire alternators use 12 volts from the ignition switch to energize the charging circuit, which is why these alternators begin charging the instant the engine is running. Most aftermarket one-wire alternators are designed so they can be used as either one-wire or three-wire installations.
A good ground cable between...
A good ground cable between the battery and the engine is essential, but so are several additional grounds between the engine and the body and the body and the frame. There was a good reason the factory placed those ground straps between the engine and the body. So now you should replace all those straps that you removed before you knew better.
Go to Ground
Electrical systems are very simple. For all domestic, 12-bolt negative ground circuits, you have a power (+) side and a ground (-) side. The most basic circuit feeds power through a wire to the load, like a light bulb, and then must complete the connection back to the negative side of the battery. Without this return side of ground, the circuit is incomplete, current will not flow, and the bulb will not light. What most car crafters overlook is the ground side of the circuit. We've seen this happen to all kinds of circuits, such as with a simple electric fuel pump wired with an adequate 8-gauge wire on the positive side but then handicapped with a tiny, 14-gauge ground wire. The ground wire was badly corroded from heat and severely limited the output of the electric pump because the smaller ground could not support the current draw back to the battery.
We've also experienced bad grounds in our Chevelle after installing a set of electrical gauges. We noticed that with the engine running, when we turned the headlights on, the in-cockpit voltmeter would drop roughly half a volt. Plus, switching the headlights on would make the engine temperature gauge read higher by 10 degrees. Clearly, we had a poor ground between the body and the battery because all those factory ground straps between the engine, body, and frame had long since disappeared. We fabricated several new grounds among the body, frame, and engine, and the voltage fluctuation (and resistance) disappeared. More importantly, both the temp and voltmeters are now more accurate.