Is it Your Battery or Your Alternator?

how to tell if alternator is bad

It’s one of those annoying occurrences that inevitably happens to everyone. You turn the key in the ignition and the car won’t start. Is the problem the battery or the alternator? Here’s how you can tell if the alternator or car battery is to blame.

Battery issues?

Consider when the battery was installed. If you haven’t changed it since you bought the car four to five years ago, chances are that’s the issue. Fortunately, it’s not expensive to replace – a typical car battery only costs from $50 to $120, depending on the make and model of the car. There are also ways you can  help improve the life of your car battery.

It’s the battery that supplies the power that starts your car and allows your vehicle’s electrical system to run. Unfortunately, as it ages it becomes less able to retain a charge because the metal inside ultimately corrodes. So even if the alternator is working perfectly, the level of battery charge diminishes, falling to a level where it is unable to start the car.

How to check your car battery

First, check the dashboard battery gauge. Even without starting the car, is the battery still sending out a charge? If this is dim, something is likely going on with your battery. Try turning on your windshield wipers, lights or automatic windows. Then make sure these are all turned off and once again try to start the car.

If it still won’t start, use a rag to carefully wipe away any corrosion on the battery and have someone jump-start it. After running the motor for a while, turn the car off. If you can’t get it to restart, this is a sign the alternator is doing its job of keeping the battery working while the motor is running, but the battery is incapable of retaining the charge without the aid of the alternator.

How to tell if the alternator is the problem

If the battery is working, it’s time to take a closer look at the alternator. There are certain signs of a bad alternator to look for:

  • While running the car, take note of the interior lights and how bright these appear. If the dashboard gradually dims, that likely means the alternator is at fault.
  • Consider your headlights. Do these run brighter as you accelerate but then dim as you pull up to a red light? If so, the alternator is likely not doing its job of keeping the battery adequately charged.
  • Did you hear a growling sound before the trouble started? That sometimes occurs before an alternator fails. Are there signs your alternator is overheating, such as the smell of burning rubber or hot wires? If so, it’s time to replace it.
  • Some may recommend running the engine with the negative battery cable disconnected to test the alternator. However, this is not a good idea because it could damage the electrical system of your vehicle and cause greater problems.

If you notice any of these symptoms, you might need to replace your alternator. Depending on your car, replacing an alternator can be an expensive repair. Make sure you have the right car insurance that covers you in case you do have a bad alternator.