GM 2 Wire Alternator Wiring Diagram

The GM 2 wire alternator has been a popular choice for hot rodders and race enthusiasts alike for decades. This alternator is easy to install, produces ample charging power, and is readily available. However, wiring it correctly can be a bit confusing, especially for those who are new to electrical systems. In this article, we will provide a comprehensive guide on how to properly wire a GM 2 wire alternator.

What is a GM 2 Wire Alternator?

A GM 2 wire alternator, also known as a SI alternator, is a type of alternator that was used on most GM vehicles from the mid-70s to the early 90s. It is called a 2 wire alternator because it only has two connections, one is the battery terminal and the other is the voltage sensing wire. This type of alternator is ideal for those who want a simple and reliable charging system for their vehicle.

How Does a GM 2 Wire Alternator Work?

The GM 2 wire alternator works by using two internal circuits to produce charging power. The first circuit is the charging output circuit, which produces the actual charging power. The second circuit is the voltage sensing circuit, which senses the voltage of the battery and adjusts the charging output accordingly.

When the engine is started, the alternator begins to produce charging power. This charging power is sent to the battery through the battery terminal connection. The voltage sensing wire is connected to the battery positive terminal and senses the voltage of the battery. If the battery voltage is low, the voltage sensing circuit tells the alternator to produce more charging power. If the battery voltage is high, the voltage sensing circuit tells the alternator to produce less charging power.

Wiring a GM 2 Wire Alternator

Step 1: Disconnect the Battery

Before beginning any wiring work, it is important to disconnect the battery. This will prevent any accidental shorts and protect both the wiring and the battery.

Step 2: Identify the Connections

Identifying the connections on the GM 2 wire alternator is fairly simple. The battery terminal connection is a thick wire that is usually red and is connected to the battery positive terminal. The voltage sensing wire is a thin wire that is usually brown or brown with a white stripe and is connected to the battery positive terminal or a switched ignition source.

Step 3: Connect the Battery Terminal Wire

The battery terminal wire should be connected to the battery positive terminal using a ring terminal. This connection should be tight and secure to prevent any accidental shorts.

Step 4: Connect the Voltage Sensing Wire

The voltage sensing wire should be connected to the battery positive terminal or a switched ignition source using a spade terminal. This connection should be tight and secure to prevent any accidental shorts.

Step 5: Run the Ground Wire

In most cases, the GM 2 wire alternator does not require a separate ground wire. However, if the alternator does not have a good ground, it may not work properly. If this is the case, a separate ground wire should be run from the alternator case to a good ground on the vehicle.

FAQs

Question Answer
What is the output of a GM 2 wire alternator? The output of a GM 2 wire alternator is typically around 60-100 amps.
Can a GM 2 wire alternator be used with a one wire setup? Yes, a GM 2 wire alternator can be used with a one wire setup by connecting the battery terminal wire directly to the battery positive terminal and omitting the voltage sensing wire.
Can a GM 2 wire alternator be used with a 3 wire setup? Yes, a GM 2 wire alternator can be used with a 3 wire setup by adding a separate wire for the exciter circuit.
What is the difference between a GM 2 wire alternator and a GM 1 wire alternator? The main difference between a GM 2 wire alternator and a GM 1 wire alternator is that the 1 wire alternator only has one wire, which is the battery terminal wire. The voltage sensing is done internally, which makes wiring much simpler.
Do I need to use a diode with a GM 2 wire alternator? No, a diode is not required with a GM 2 wire alternator. The voltage sensing circuit within the alternator serves the same purpose as a diode.

Conclusion

Wiring a GM 2 wire alternator may seem daunting at first, but it is actually very simple. By following the steps outlined in this article, you can ensure that your alternator is wired correctly and functioning properly. If you have any questions or concerns about wiring your GM 2 wire alternator, consult a professional electrician or mechanic.