by William Collins

Created on: May 23, 2009   Last Updated: June 25, 2009

An alternator is a device that uses mechanical energy to charge your car's battery. Although there are many different designs of alternators, the fundamental principles are the same in all of them. They take mechanical energy via a rotating belt and convert it into AC (alternating current): electricity that fluctuates from a high peak voltage to a negative peak voltage. Then this AC electricity is converted to DC (direct current) -the kind you car can use in its battery. This article will explain how to rebuild one of the most popular alternators built: the Delco SI series.

If you have a little mechanical ability and a few tools you should be able to rebuild an alternator without much difficulty. I will suggest where you will benefit from photos or notes by including the words ('SNAP') in the text.

THE TOOLS

A set of 1/4 inch drive sockets.
Phillips screwdriver
Flat screwdriver
Large paper clip
Large "C" clamp or arbor press
Small gear puller
A set of 1/2 drive sockets
Heat sink compound (Radio Shack)
Alternator rebuild kit
A small strip of 800 grit wet/dry sandpaper
Paper and pencil or a digital camera

The first thing you should do is disconnect the car battery.
Look behind the alternator and ('SNAP') note the wiring that is connected back there. It is simple wiring that is difficult to wire the wrong way.

A large red 10 gauge wire connects the large terminal of the alternator to battery power. A large black 10 gauge wire connects the case of the alternator to ground. There are two other 14 gauge wires inside a molded connector that only fit in the connector slots. No worries here, the left terminal (#1) goes to the alternator '=warning light, (often referred to as the 'idiot light') and the right terminal (#2) goes to the battery. It supplies sensing voltage to the voltage regulator. Speaking of rotors, here are the basic parts of an alternator.

THE PARTS

The pulley and fan. They are bolted to the front of the alternator.The case, is composed of two halves held together with 3 long bolts. If this part is cracked or broken, just get a new alternator, or another used case.

The rotor is the part that spins around. It provides the electromagnetic field that is picked up by the stator. The stator is composed of many windings of wire that encircle the spinning rotor. Every time a finger of the rotor with its magnetic force cuts across one of the stator windings, it produces a spike of electrical energy.

Bearings - there are two of them, one on each half

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