Which part of the charging system is likely faulty when the output voltage is too high?

In a vehicle's charging system, the part responsible for regulating the output voltage to maintain a consistent level for the battery and electronics is the voltage regulator. When the output voltage is too high, it indicates that the regulator is not functioning correctly. The regulator's job is to control the voltage produced by the alternator, ensuring it stays within the manufacturer's specified limits (usually around 13.5 to 14.5 volts). If the voltage regulator fails, it may allow excessive voltage to pass through, which can lead to overheating, potential damage to the battery, and other electrical components.

The alternator is responsible for producing electricity, but it needs the voltage regulator to ensure that the output is appropriate. A faulty battery would typically cause low output voltage, rather than high. The starter motor's primary function is to start the engine and does not play a role in regulating the charging system's voltage. Thus, a malfunctioning voltage regulator would be the most logical cause of excessively high output voltage in the charging system.