Why Won't My Car Start? Is the Battery, Starter or Alternator at Fault?

Today we'll be talking about how your car's battery, starter and alternator work together to turn over your engine, power your electrical system and recharge your battery so that it can continue working. We'll also tackle a few of your most common questions regarding engine failure and help you determine which of these three components is responsible.

How Does a Battery and Starter Work to Turn Over Your Engine?

In order for your engine to start, it needs to be turned at a fast enough speed to suck fuel and air into the engine's cylinders and compress it. When you engage your car's engine, a signal is sent to your vehicle's battery causing a chemical reaction, which creates electrical energy. The shaft of your vehicle's starter contains a gear wheel which connects with a large gear ring around the rim of the engine's flywheel. Your starter uses electrical power from the battery to turn the engine, delivering fuel into the engine cylinder and compressing it.

What Does an Alternator Do?

While your car's battery is responsible for starting your car when it's turned off, it's the alternator that provides the direct current (DC) power needed to run your vehicle’s electronics while you're driving. This includes things like headlights, power steering, power windows, windshield wipers, dashboard instruments and radios. Your alternator is also responsible for recharging your battery while you drive. It does this by converting the mechanical energy created by driving into electrical energy.

Why Won't Your Engine Start?

If you're having a hard time turning over your engine, there's a good chance it's because of issues with your battery, starter or alternator. But how can you tell which one? Fortunately, there are a number of signs that can help you determine which component is causing the issue.

Signs That Your Battery is Dead

• When you attempt to start the car, there is a low whining sound.
• If jump starting gets your engine started and running, but the car will not start again once you turn it off, the battery is probably the problem. In this case, the alternator is doing its job of keeping the battery going once it has been jumped, but the battery can’t hold a charge when the alternator is shut off.

Signs That Your Starter Has Failed

• When you try starting the car, there is a clicking, whirring or grinding noise.
• Try jump starting your car. If you can't get the engine to turn over after multiple attempts, that's a good sign that the starter is at fault.

Signs That Your Alternator Has Failed

• You can often hear a growling sound right before your alternator goes out.
• You may notice a burning rubber smell caused by your alternator overheating.
• Your headlights or your dash lights may flicker or get extra dim or bright.
• Your gauges may start behaving strangely.
• If you jump start your car successfully, but the engine dies right after the jump, it's most likely the alternator. (Note: Do not try to test the alternator by removing the negative battery cable with the engine running. This could damage your car or truck's electrical systems).

Batteries Plus Will Test Your Battery, Starter and Alternator for Free

If you're experiencing any of the issues mentioned above, there's an easy way to get answers. Just bring your vehicle to Batteries Plus and have it tested, free of charge. We’ll test your battery's Cold Cranking Amps and voltage, as well as your car's starter and alternator to help you determine the problem. Call your nearest store for more info.

If it turns out to be battery-related, our experts can help you find the best replacement option for your make and model. Plus, we offer free installation on most vehicles at most of our locations. Find your nearest Batteries Plus store, or shop our selection of car and truck batteries online. If you need a battery installed, you can cut down on your wait time by scheduling an arrival time that's convenient for you. Have another auto issue? Visit our automotive center for headlight bulbs, wiper blades, key fob replacement service and more.