Introduction

This page provides information in regards to Toyota alternators basic operation and wiring.

This page will focus on the Toyota alternator with inbuilt regulator, however some information maybe valid for generic alternators.

Alternator Function

The function of the alternator is to supply electrical energy to support the electrical loads in the vehicle's electrical system.  These loads include the electronic fuel injection system, radio, lights, defogger and more.  As a number of these loads are critical (i.e. fuel injection system) it is important that the system functions well.

It is worth noting that under normal operating conditions the alternator is responsible for supplying all of the electrical energy required for the vehicle systems, the battery is only used to help in filtering out voltage spikes and supplying small amounts of extra current during short duration events such as when heavy electrical loads are turned on (e.g electric engine cooling fans turning on).

Of course the alternator is also responsible for charging the battery after the engine has been started, to replace the electrical energy that used to start the engine.

Alternator Operation

In general terms the alternator is driven by the engine to turn mechanical energy into electrical energy.  I won't explore the details in regards to how the alternator generates electrical energy from mechanical energy in this article, however I will briefly explore how and why the output of the alternator is regulated.

As the alternator is required to (ideally) output a fixed voltage regardless of the electrical load (current) of the vehicle system and the engine RPM it makes sense that there needs to be a system that controls the alternator to ensure that the alternator voltage output remains stable and consistent across the wide range of operating conditions that are likely to be experienced. 

The alternator 'regulator' is the component that is  responsible for controlling the alternator to achieve the desired operation.

Alternator with Inbuilt Regulator

This section will discuss the Toyota alternator with inbuilt regulator and the wiring associated with the alternator and regulator.

Since the early 1980's (~1983) Toyota have used an alternator with an inbuilt regulator, prior to this the regulator was a module that was mounted external to the alternator.  As mentioned previously this page will focus on the alternator with inbuilt regulator predominately.

Alternator with Inbuilt Regulator Pinouts

There are a number of different 3 pin regulator plugs. 

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