How To

How to Check if Your Alternator is Charging Your Battery

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.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

Multimeter or voltage meter
Car battery
Car alternator

Step 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.
Step 2

Ensure the connections are secure between the alternator and battery, after turning off the car. Also, check the alternator belt for damage.
Step 3

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

Comments

twrilyboy01 said

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on 3/8/2009 i have a problem just like this in my 01 subaru legacy GT. I just replaced the alternator and the battery. but the battery keeps dying. I took it to autozone and they charged it for me and the same thing happended. anyone have an idea what the problem could be? any help would be great!