What is a common indication of a faulty alternator?

A common indication of a faulty alternator is when headlights dim while the engine is idling. The alternator is responsible for charging the battery and supplying power to the vehicle’s electrical systems while the engine is running. If the alternator is failing or not producing enough voltage, it can cause insufficient power to be delivered to components such as the headlights. When the engine speed decreases, the alternator's output may drop, leading the headlights to dim significantly, especially at idle, when electrical demand may exceed the available power from the alternator.

This symptom can often be noticed during situations where there are additional electrical loads also drawing power, such as when running air conditioning or using accessories. Therefore, the dimming of headlights is a clear and common sign that the alternator is not functioning correctly. Understanding this symptom can assist in diagnosing charging system issues effectively.