Your Car 101 (Series) - How do I know my alternator is bad?

Problems Starting?

That is a very easy DIY (Do It Yourself) check.  First, let's understand the basics of the alternator, and it's relationship with your car and your battery.

The Battery

Your battery is what starts your car.  It stores enough "energy" to get your motor moving.  That is why the CCA (Cold Cranking Amps) is important when choosing a replacement battery.  The battery also provides a backup for your car when the car sees a larger draw on it's electrical system than what the alternator can handle.  This can be seen with people that have a large subwoofer/amplifier system.  You can see their headlights or interior lights dim each time the bass hits, or when the amplifier puts a huge draw on the electrical system.

The Alternator

The alternator keeps the car running and recharges your battery after the car starts.

Checking the Alternator

SO, the quickest and easiest way to check your alternator is to

       1) Start the car.
       2) Once running at idle, disconnect your battery.

Understanding the basic principles above, two things will happen.  If the alternator is bad, the car will shut off since there is no longer electricity being generated for the car to operate.  If the alternator is good, the car will stay running and your issue may be elsewhere.  If the car won't start at all, even with a jump on the battery, then you might check the battery.

- Bryan Lin | CEO, The Motorsports Authority, Inc. | www.MSAStore.com