Car Alternator Wiring Diagram and Connection ( 2 ,3 ,4 Wire)

An alternator is an essential component of a car's electrical system. Its main function is to provide the power supply to the car's electrical systems and recharge the battery while the engine is running. 

The Alternators used in Cars can be classified into different types based on the number of terminals they have. For example, Two-Terminal Alternator, Three-Terminal Alternator, Four-Terminal Alternator, Five-Terminal Alternator, etc. 

The number of terminals determines the type of electrical connections and functions the alternator can perform. In this article, we are going to see the wiring diagram and connection of those different types of alternators.

2 Wire or 2 Pin Alternator Wiring Diagram

Here, you can see the wiring diagram of a 2 Wire Alternator.

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Connection Description

You can see the 2-Pin Alternator has two terminals - 1. Positive Terminal for Battery(B+) 2. Positive Terminal for Dash light(D+). Here we did not consider any terminal for the negative connection as it is connected to the alternator metallic body. You can say, in actuality, this alternator has three terminals for connection.

In some alternators, there are only positive and negative terminals for the connection, there is no connection for Dash Light or Indicating Light.

Anyway as per the above wiring diagram, the positive terminal is connected to the positive terminal of the battery. The D+ terminal is connected to the Dash Light. the other terminal of the light will be connected to the Switch or Fuse Box. 

The negative terminal of the battery and the metallic body of the alternator is to be connected to the chassis ground to make a connection between them as we know the negative terminal of all the electrical equipment is to be connected to the chassis ground in the vehicle.

3 Wire or 3 Pin Alternator Wiring Diagram

Here, you can see the wiring diagram of a 3 Wire Alternator.

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Connection Description

As you can see the 3-pin alternator has three terminals named as 'BAT' (Battery), '1', and '2'. In some alternators, it may be named as Battery, Field, and Sense or Battery(B+), Ignition Switch(IG), and Warning Lamp(WL).

As per the above wiring diagram, the terminal 'BAT' is connected to the positive terminal of the battery. The terminal '1' is connected to the Indicating Lamp or Warning Lamp. Terminal '2' is directly connected to the positive terminal of the battery. 

Remember that, if the alternator has the 'IG' or Ignition terminal then it should be connected to the Ignition switch instead of directly connected to the battery.

Here also, the negative terminal of the battery and the metallic body of the alternator is to be connected to the chassis ground to make a connection between them.

4 Wire or 4 Pin Alternator Wiring Diagram

Here, you can see the wiring diagram of a 4 Wire Alternator.

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Connection Description

The 4 Pin Alternator has four terminals named as 'B+'(battery positive), 'IG'(Ignition Switch), 'S'(Sensing Voltage), and 'L'(Lamp Ground). Some alternators may have different names according to the manufacturer. It is best to follow the product manual. If you count the grounded negative terminal, then it can be called a 5 Terminal Alternator. But generally, we did not count the negative terminal as it connected to the body.

As per the above wiring diagram, terminal 'B+' is to be connected to the positive terminal of the battery. Terminal 'IG' is to be connected to the Ignition Switch. Terminal 'L' is to be connected to the negative terminal of the Lamp and the positive terminal of the lamp is to be connected to the battery, switch, or fuse box. Terminal 'S' is to be directly connected to the positive terminal of the battery.

Here also, the metallic body of the alternator and the negative terminal of the battery is to be connected to the chassis ground to make a connection between them.

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