Alternator Charging Problems

Alternator charging problems can occur in five general areas:

  • Battery failure, causing too much draw from the alternator, which causes overheating and imminent failure.
  • A loose alternator belt causing slippage.
  • Too much draw or having accessory equipment such as a stereo amplifier that requires higher amperage than the alternator can supply on a continuous basis.
  • Corroded wires or the wrong size wires being used, causing high resistance and resulting in a voltage drop.
  • Voltage regulator problems causing an over or under charge condition.

A battery that has a bad cell will not be able to take a complete charge and has a continuous voltage drain. This happens as a battery gets older or was discharged too low too many times. When this happens the engine will labor when started and sounds like the battery is low, usually after the car was at rest for several hours. A battery with a bad cell will cause the alternator to work much harder to continuously attempt to charge the battery, which causes the alternator to overheat and fail.

A loose alternator belt will cause the alternator to slip, especially when a heavier draw is placed on the alternator, such as turning a stereo on or the headlights and air conditioning.

An alternator is always installed from the factory with just the right amount of amperage output, which is compatible with the equipment installed in the car. The addition of a stereo amplifier or another accessory that requires more amperage than the alternator is able to produce on a continuous basis will cause charging problems. Ultimately it can cause the alternator to fail.

Corroded wires are a cause of low voltage, causing a slow charge rate. The positive or negative cable at the battery are the prime suspects. A corroded cable will cause excessive resistance in the wire, which causes the voltage drop. Too small a wire will do the same thing. Wires come in different gauges for different loads. For example, if a 16-gauge wire is used for a radiator fan, which draws 20 amps. The voltage will drop due to the resistance. The wire gets extremely hot, causing a possible fire. Loose connections can also cause excessive resistance or a loose ground wire.

The voltage regulator in the alternator can fail and result in low alternator output. A failure in the diodes will cause a similar problem. Alternator output should be checked to diagnose this particular problem.

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