Is It My Battery or Alternator?

There are a few different ways to tell if your alternator or battery is bad.

If your battery is dead and won’t hold a charge, it’s probably time for a new one.

If your car starts up fine but doesn’t have enough power to stay running, you may need to replace the alternator.

If you’re hearing weird noises from under the hood, this could be an indication of an issue with either your alternator or battery.

why does it matter which one is broken?

You may wonder why it’s important to know which component is broken. Well, if one component is broken and the other isn’t, you can choose whether to replace them separately or together.

If both parts are working properly and you only need to replace one of them, you have a few options:

  • You can replace only the battery and not the alternator.
  • You can replace only the alternator and not the battery.
  • You can replace both components at once.

If you decide to go with option 1 or 2 above—replacing just one of your parts—you’ll save yourself some time since neither component needs to be removed during replacement.

Of course if you’re going for option 3 (replacing both), then removing everything may be necessary before starting work on either part in particular; however this requires more skill from an auto mechanic than simply replacing either component alone does!

Symptoms of a Bad Alternator

Your vehicle will not start or will shut off while driving.

Your vehicle will not charge.

Your vehicle will not idle, idle low, or idle high.

Your vehicle won’t accelerate properly when you press the gas pedal.

Your transmission shifts roughly and/or hesitates between gears.

You experience difficulty turning on lights, accessories, radio and other electrical devices in your car (for example: lights do not turn on).

Symptoms of a Bad Battery

If your battery is going bad, it may start to show signs of trouble. Some symptoms of a bad battery include:

The battery will not hold a charge. If you can’t drive your car for an extended period of time without having to recharge the battery, this could be a sign of a dying or damaged one.

It won’t start the engine at all

It won’t charge at all even when plugged into an outlet with power turned on

Testing for a Bad Battery

There are several ways to test if your battery is at fault, including:

Checking the voltage of your battery: A healthy 12-volt car battery should typically be around 12.6 volts when charged and in good condition, with a fully charged capacity of 55 to 70 percent. If your car’s battery is more than three years old, it may have lost its ability to hold a charge and need replacing.

Checking the charging system of your car using an auto voltmeter; this will tell you if there are any problems with the alternator or wiring in general.

Testing for any corrosion that could be hindering current flow; this can often be seen as black marks on top of posts (or terminals) where cables connect to them.

Testing for a Bad Alternator

In order to test your alternator, you’ll need a multimeter.

It’s important that you test all three spots in this process so that you can rule out a defective battery or bad connections. The voltage at the battery should be roughly between 12 and 14 volts.

The second leg of the circuit is at the alternator itself; here, you should see anywhere from 8 to 13 volts depending on how much current is going through it.

The third spot is where there should be no charge flowing through—if there’s still some residual charge left over from when your car was running, then make sure not to touch anything metal while doing this part of testing!

The next step is checking for voltage drop across all three points with both engine off and idling; if any of these readings are below 9V then something needs repairs.

Don’t delay replace battery or alternator

Don’t delay! If you suspect your battery or alternator is giving out, get it replaced right away. Batteries can be found at your local auto parts store and installed by the staff there. Alternators may require more specialized repair services that can be obtained by contacting a mechanic in your area.

How long will a new battery or alternator last?

It depends on the quality of the original unit, how well you take care of it (don’t let it run down completely), and other factors like where you live.

Before replacing anything make sure that’s actually what needs to be fixed. Think about what other symptoms might indicate an issue with either your battery or alternator:


A bad alternator can be pretty easy to spot. The most obvious sign is a car that won’t start. If your car’s battery dies, you can get it recharged, but if the alternator isn’t functioning properly, it will not be able to charge the battery again.

Alternator problems can also cause electrical issues. If your headlights suddenly dim or go out entirely while you’re driving at night, it might be an indicator of an alternator issue.

This is because when the alternator stops working properly, it won’t be able to provide enough electricity for all of your vehicle’s electrical needs—including powering your headlights.

A bad battery can also be easy to identify when it comes time for you to start your car and nothing happens.

If you have a dead battery and can’t get it recharged, then there’s no way for you to drive anywhere until you get a new one installed.

Steven Hatman
Steven Hatman

We break down every information into easy-to-understand articles that cover all the categories anyone who owns a car needs to know about, such as oil , brakes , tires and etc. Our car guide is free and updated regularly for you to use as a resource, not only when you have an issue with your car but even before buying a new or used car! We also give tips on what to look for in each category or part of your vehicle.