Genuine OEM Volkswagen Voltage Regulator, part number 028903803F. This voltage regulator's function is to control the output voltage of the alternator, ensuring it remains within the correct range for charging the battery and powering the vehicle's electrical systems. It is part of the alternator assembly. Manufactured to strict tolerances for reliable electrical performance. Genuine OEM voltage regulators are critical for maintaining stable electrical power, preventing overcharging or undercharging of the battery, and protecting sensitive electronics.