When the alternator light comes on, what does it indicate?

When the alternator light comes on, it typically signifies an issue with the vehicle's electrical system, particularly that the alternator is not functioning properly. The alternator is responsible for charging the battery while the engine runs and providing power to the electrical components of the vehicle.

If the alternator is failing or if there's an issue with the wiring or connections within the electrical system, the alternator will not adequately charge the battery. This can lead to a decrease in electrical power and may ultimately cause the car to stall or not start at all. Thus, when this light illuminates, it serves as a warning to the driver to investigate and resolve the problem before it leads to more significant issues.

The other options do not relate to the specific warning indicated by the alternator light. For example, a battery being fully charged does not trigger this light; rather, it indicates that the battery may be losing charge. Similarly, maintenance needs for brakes or the engine overheating are unrelated to the functioning of the alternator itself.