The word alternator sounds a bit like terminator and you should fear hearing a mechanic mentioning it with equal dread.

Alternator problems can be difficult to sort out and expensive. The alternator is basically a simple mechanism that converts mechanical energy generated by the engine to electrical (alternating current) energy to power your car's electrical systems and charge the battery. Tell tale signs of alternator problems are if your battery keeps running down or is reading a low charge even if it isn't that old.

A quick way to check the charging system is to start the car and turn on the headlights. If the headlights are dim, it indicates the lights are running off the battery and little power is being produced by the alternator. If the lights get brighter as you rev the engine, it means the alternator is producing some current but may not be producing enough to keep the battery properly charged.

If the lights have normal brightness and don't change intensity as the engine is revved, your charging system is functioning normally.

You can also check the charging system by connecting the leads of a voltmeter to the battery. When the engine starts, the charging voltage should jump to about 14.5 or higher. If the reading doesn't change or rises less than a volt, you have a charging problem that will require further diagnosis. Alternators are tough but can be damaged by excess heat or overwork. They can also be damaged by sudden voltage overloads. In every alternator is a "diode trio" that converts the alternator's AC (alternating current) output to DC (direct current). If one or more of these diodes fail, the alternator's amperage output will be reduced. It may continue to produce some current, but not enough to keep the battery fully charged.

Most mechanics have test equipment that can identify these kind of problems. So if you suspect a weak alternator, you should have it tested to see if it needs replacing.

Mechanics generally do not repair or rebuild alternators because it's too time consuming and requires special parts. Most will replace your old unit with a new one.

If you are replacing an alternator yourself, always disconnect the battery before unhooking the wiring on the alternator. If you don't you run the risk of causing a short circuit which could damage components or start a fire.

The alternator drive belt should be inspected at this time, and replaced if it is cracked, oil soaked, glazed, badly worn or otherwise damaged. The belt should also be adjusted for proper tension. Too much tension can overload the alternator's bearings and shorten its life while too little can allow the belt to slip.

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