Bad Alternator vs Bad Battery: How to Tell Which Is to Blame When Your Car Won’t Start

Everyone has been there before; it’s raining outside, and you need to get home fast. You put the key in the ignition to hear the engine start, and to your dismay, your car won’t turn over.

Your car not being able to turn over can be caused by a litany of reasons, but the most common come between two components: Your battery and your alternator.

Unfortunately, for an average joe, it can be difficult to tell the difference. But here is a quick guide to being able to tell between a bad alternator vs a bad battery situation.

Signs of A Bad Battery

Your car battery fuels pretty much everything else that the gas doesn’t in your car and is something that should be immediately replaced when it shows signs of faulty behavior.

There are at least 7 factors to consider when buying car batteries if you want your battery to last a long time, then you have to properly take care of your battery.

A bad battery will usually give you several signs that it’s on its way out:

Battery Corrosion

On a normal, healthy battery, the terminals on it should be relatively clean with no signs of corrosion. However, if you see corrosion on your battery, chances are the battery is damaged and/or leaking.

Lights and Other electronics

If your lights in your car fixtures like your dashboard and headlights seem dim, if there are no car sounds when turned on, or your engine seems sluggish to turn on, chances are your battery needs to change.

Signs of A Bad Alternator

An alternator is supposed to last for as long as the car is operable. However, it is subject to several weaknesses that can cause it to falter. 

Your alternator is connected to other parts that do get dirty and eroded due to the heat of the engine and leftover residue. So here are some of the signs of a bad alternator:

Weird Noises Coming from the Engine

If there are noises that sound like squealing or screeching coming from your engine area usually comes from your alternator bearings. These noises usually get louder when the radio comes on also.


Your car might work and turn over, but when using it might stall the car. If this happens, it’s due to the alternator. 

These are the most definitive signs, but there are others that are similar to the signs of a bad battery as well, so you should look for these first because the others might lead you away from the real problem.

Knowing a Bad Alternator Vs Bad Battery

When trying to understand the bad alternator vs bad battery, do your diligence to identify the signs that are separate from each other first. This will help you reduce the options.

Once you identify the problem, the fix should be simple. Learn the signs of your car so you can tell the difference.

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