How to Tell if You Have a Bad Car Battery or Alternator

Mechanic's hand pulling up an car old battery for replacement

Is it a bad car battery or an alternator?

Picture this: you’re running behind on a chilly morning and need to get to work. You pack your stuff and head to your car, get behind the wheel, and…it won’t start. You turn the key a few times and nothing’s happening. You know there’s plenty of gas, which means it could probably be one or two things: a bad car battery or alternator. 

But how do you know which one is the problem? As it turns out, both car batteries and alternators have a few tell-tale signs to show that they’re about to fail (and sometimes they’re pretty similar). As a car owner, one of the chief responsibilities you have is to keep a close eye on your vehicle to head off any problems with your car.

Let’s look at the symptoms of a bad battery and alternator and what to do when one is keeping you from reaching your destination.

Car batteries can typically last between three to five years, but there are plenty of factors that shorten their lifespan. Cold weather can reduce their effectiveness, as can connecting extra accessories like internal power inverters. If you’ve noticed one or more of the following symptoms, it might mean it’s time to replace your car battery:

  • Your car has trouble starting.
  • Your car won’t hold a charge for long.
  • Your headlights and taillights are dim or flicker.
  • Your interior and dashboard lights flicker or are dim.
  • Warning lights on your dashboard signal battery problems.
  • Corrosion has started to form around the contact points on your battery.

Signs of a Bad Alternator

Alternators help keep your car battery charged while the vehicle’s running. A failing alternator means the battery won’t recharge while the engine’s on. If you drive all day long, you typically won’t have a problem with your battery because the alternator has enough drive time to recharge it. Very short daily commutes or leaving the lights on overnight will drain your battery.

The best way to tell that your alternator is bad is if your car quickly dies after a jump start. Most alternators should provide the necessary current to keep going even with a bad battery. If this isn’t the case, the alternator needs to be fixed. Other signs can include:

  • The voltage meter on your dashboard starts to drop.
  • Your car starts to vibrate while you’re driving.

If you see low voltage on the battery after you charge it up and the car has been running awhile, it’s a sign that something’s wrong with your alternator.

You’ve found the issue, now what do you do?

If either the alternator or battery is bad, you’ve got to replace it. You can purchase a battery from an auto parts store. They may even replace it for you as part of the cost. Otherwise, you can install it yourself.

Replacing an alternator is a little trickier and might require a certified mechanic. How much you pay for repairs will depend on the make and model of your vehicle, parts costs, and labor charges.

Auto insurance won’t cover the cost of replacing either the battery or the alternator, as these are considered normal expenses under car maintenance, but it can help offset the price of having your car towed or roadside services (if you have appropriate coverage).

Find the Right Car Insurance for Your Needs with SelectQuote’s Help

If you’re worried about being stranded due to a bad battery or alternator, it helps to have car insurance with the right kind of coverage. SelectQuote can help you shop for car insurance that covers all your needs, including roadside service. Our proprietary technology compares prices from dozens of the most respected auto insurance companies around and can deliver a quote that fits your budget.

Insuring more than your car? Be sure to ask about bundling car and home policies for maximum savings.

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