Final answer:
A constant output of 16.0 volts from the alternator likely indicates a failed alternator, as it should normally produce close to 12.0 volts to maintain the health of the battery and other electrical components.
Step-by-step explanation:
If a vehicle's battery fails prematurely and a charging system output test shows that the alternator is producing a constant 16.0 volts, this could indicate a failed alternator. The alternator's job is to charge the battery and power the electrical system while the engine is running. A properly functioning alternator should maintain the system voltage within a range close to 12.0 volts, often between 13.5 and 14.5 volts, to protect the battery and the electrical components of the vehicle. If the alternator produces too much voltage, it can cause excessive charging and damage to the battery, leading to premature failure.
Vehicles are designed to operate on a specific voltage, typically around 12.0 volts, as indicated by the examples showing the ordinary connection of headlights and starter motors in parallel in a 12.0-V system. When an alternator produces too high a voltage, it can lead to various electrical issues, including the potential for battery damage.