How to Check if Your Alternator is Charging Your Battery

Written by ehow cars editor
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When diagnosing battery trouble, you must check the alternator to see if it is charging correctly. If the alternator is not working right, the battery slowly drains down. If your battery is drained, it will not run the important electrical systems in your car. Read on to learn how to check if your alternator is charging your battery.

Skill level:
Moderately Easy

Things you need

  • Multimeter or voltage meter
  • Car battery
  • Car alternator

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  1. 1

    Start your car. If the headlights are dim, the alternator is going out. Turn off your lights, radio, air conditioner or any other running electrical system.

  2. 2

    Ensure the connections are secure between the alternator and battery, after turning off the car. Also, check the alternator belt for damage.

  3. 3

    Turn on the ignition, again. If your car doesn't start, you must use a battery charger.

  4. 4

    Connect a multimeter or voltage meter to test the alternator. Idle the engine. Check to see how many volts are showing on the meter. There should be 13.6 to 14.3 volts showing.

  5. 5

    Talk to your mechanic if your alternator is not charging your battery. You can trade in your alternator and your mechanic can give you a new or rebuilt alternator.

Tips and warnings

  • If the headlights get brighter as you rev the engine, your alternator is likely charging the battery.
  • Make sure you wear protective eyewear when working under the hood of a car.
  • Once you realize that your alternator is going out, do not turn the car off until you get to your destination or you may need a battery charger to start it up.

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