Testing Alternator and RegulatorStart the engine and run it at about 3000 rpm with all electrical accessories turned off. Set the voltmeter to the DCV scale and measure the voltage between the positive and negative terminals of the battery. Make sure that the tester is connected to clean areas of the terminals. A reading between 13.5 to 14.5 volts indicates a correctly operating system. A reading higher than 14.5 volts most likely indicates a faulty voltage regulator. A reading below 13.5 volts means that the battery is not being adequately charged because either the regulator or the alternator is faulty. To determine which, keep the car running at about 3000 rpm and turn on all electrical accessories, then check voltage across the battery. A reading that is the same as the first most likely indicates a faulty regulator. A reading that is lower most likely indicates a faulty alternator. |
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