How to Identify Alternator Terminals

Written by mark robinson
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How to Identify Alternator Terminals
An automobile cannot operate on battery power alone. (New car petrol engines image by Christopher Dodge from

The alternator is one of many key components in a vehicle's overall operation. This component converts the mechanical energy of the engine transmitted by the engine's serpentine belt into electricity that keeps the battery charged and powers various electric accessories. The alternator features several terminals that require proper identification for a successful installation. Connecting the wrong lead to the wrong terminal can cause damage to the alternator, as well as injury from shock.

Skill level:

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  1. 1

    Stand the alternator up on its bottom bracket with the pulley side facing toward you and the top bracket facing straight up.

  2. 2

    Face the rear of the alternator toward you, and find the threaded stud and nut on the back of the alternator near the top---the location of the output (battery positive) terminal. The battery positive lead connects to this terminal via a ring terminal connector, with the nut holding it in place.

  3. 3

    Find the voltage regulator socket located on the side of the alternator at the 3 o'clock position. The voltage regulator connector plugs into this socket.

  4. 4

    Find the threaded stud and nut near the 5 o'clock position---the location of the ground terminal connection. The ground lead attaches to this terminal. (Keep in mind that some alternators come without a ground terminal.)

Tips and warnings

  • Always disconnect the negative ground terminal cable from the battery when working on any engine component. to minimise the possibility of shock and serious injury.

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