How would you check the output of an alternator?

Measuring voltage at the battery terminals while the engine is running is an effective method to check the output of an alternator. When the engine is operating, the alternator generates electrical power to charge the battery and supply electrical systems in the vehicle. A healthy alternator should provide a voltage reading typically between 13.5 and 14.5 volts at the battery terminals. This range indicates that the alternator is functioning correctly and is able to keep the battery charged while supplying power to the vehicle’s electrical needs.

In contrast, checking the amperage rating of the alternator does not provide real-time information about its performance under load conditions. Inspecting the wiring harness for damage is important for overall electrical system health, but it does not directly measure the output capability of the alternator. Testing the battery voltage with the engine off only provides information about the battery's state of charge, not the alternator's ability to produce voltage while the engine is running. Therefore, measuring voltage at the battery while the engine is active is a direct and reliable method to assess the output of the alternator.