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ASVAB · Vehicle Systems

What is the main function of the alternator in a vehicle?

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

To generate electrical power and charge the battery while the engine runs

  1. A To generate electrical power and charge the battery while the engine runs
  2. B To cool the engine
  3. C To filter the oil
  4. D To start the engine

Why this is the answer

The ALTERNATOR generates electrical power and CHARGES THE BATTERY while the engine runs, supplying electricity to the vehicle's systems. ASVAB Auto Information tests vehicle systems. The STARTER motor cranks the engine to start it (using battery power); the ALTERNATOR then takes over, producing electricity to run the car and recharge the battery. If the alternator fails, the car runs on battery alone until it dies. Knowing the alternator charges the battery and powers electrical systems (vs the starter that starts the engine) is commonly tested.
Source: ASVAB Auto Information — Charging System

Practice more questions

This question is from our ASVAB Practice Tests practice test. Take the full practice test to test your knowledge across all Vehicle Systems and other topics.

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About this topic: Vehicle Systems

Vehicle systems questions ask how the major subsystems work together — fuel, ignition, cooling, lubrication, electrical, exhaust and drivetrain — and what symptom points to which system. You do not need mechanic-level depth, just the function of each part and the common failure signs. This is one of 9 Auto Information questions on vehicle systems, each with a full explanation on a single study page.

New to this exam? Our ASVAB exam guide explains the format, scoring, and how to prepare.

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