Voltage Regulator Problems

by Keith Allen
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As the name would suggest, the voltage regulator controls the voltage of an automobile electrical system. If the voltage regulator fails it can result in higher or lower voltage levels going from the alternator to the battery. In some situations, the voltage regulator can completely fail and break the circuit resulting in no electrical connection between the alternator and battery. Any of these conditions can result in electrical problems that can result in the car not starting.

Checking for High Voltages

High voltages can cause damage to the battery and electrical system by overcharging the system. Checking the voltage of the system requires the battery of the car to be fully charged. Attach a multimeter set to measure amps to the battery. Use clamps, if available, to attach the multimeter leads to the battery. While the battery is charging the amp meter will read more than eight amps. Once the amperage drops to eight amps the battery is fully charged and the multimeter can be switched to DC volts. A properly working voltage regulator will output 13.8 to 14.8 volts when measured across the battery poles. If the voltage is greater than 14.8 there is likely a problem with the voltage regulator. Expect the voltage to be near the higher end of the scale for cold engines and the lower end of the scale for hot engines.

Checking for Low Voltage

If the voltage measured at the battery is less than 13.8 volts, the problem could be the voltage regulator or some other portion of the electrical system. Measure the voltage at the voltage regulator and any other accessible points along the electrical system. Look for defective wiring or components that could cause a loss of power. If none are found, replace the voltage regulator and retest.

No Electrical Output

If there is no electrical output from the alternator and voltage regulator, either could be the problem. In some cars, the voltage regulator is integrated into the alternator. In those cases, the alternator will need to be replaced.

Other problems that can cause the loss of electrical power include defective drive belt for the accessories of the engine or a faulty wiring harness. Short driving trips can also cause problems similar to a low voltage situation because the cars electrical system doesn’t run long enough to recharge the battery.

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