How Do You Know If It’s a Battery Or Alternator Problem?

Published on: October 8, 2022
Written by Jonas Frank / Fact-checked by Nova Scarlett

If your car isn’t starting, it could be a battery or alternator problem. But how can you tell which one it is? If the engine is cranking but not starting, it’s more likely to be a battery problem.

If the engine is starting but the headlights are dim or flickering, it’s more likely to be an alternator problem. You’re driving along and suddenly your car dies. You try to restart it, but it won’t turn over. Now you’re stranded on the side of the road.

how do you know if it's a battery or alternator problem

But how do you know if it’s a battery or alternator problem? There are a few things you can check to see which one is the culprit.

First, check to see if all the lights in your car are working. If they’re not, then it’s probably a battery issue.

Second, try starting your car with the headlights off. If they come on, then it’s probably an alternator problem.

If you’re still not sure, the best thing to do is to take your car to a mechanic and have them diagnose the problem. They’ll be able to tell for sure which one is causing the issue and get your car back up and car running in no time!

What are the Symptoms of a Bad Battery Or Alternator?

If your car won’t start, the battery is probably dead. But if the engine turns over slowly or not at all, it could be a sign of a bad alternator. Here are some other symptoms that can help you diagnose the problem:

• A clicking noise when you turn the key in the ignition;

• Dim headlights or dashboard lights;

• A burning smell coming from under the hood;

• The battery light on your dash is lit up If any of these things are happening, it’s time to get your car checked out by a mechanic;

They’ll be able to tell for sure whether it’s the battery or alternator that needs to be replaced.

How Do You Test a Battery Or Alternator?

When testing a battery, you will need a voltmeter. To test the alternator, you will need an ammeter.

First, disconnect the negative (-) terminal of the battery.

Next, touch the red lead of your voltmeter to the positive (+) terminal of the battery and touch the black lead to the negative (-) terminal. If your reading is 12.6 volts or higher, then your battery is fine. If it’s below 12.6 volts, then your battery needs to be charged.

To test your alternator, first, make sure that all accessories in your car are turned off including lights and heater fan. With the engine running, touch the red lead of your ammeter to the positive (+) terminal on your alternator and touch the black lead to the ground (any metal part of your car). Your reading should be between 13-14 volts if everything is working properly.

What are the Common Causes of Battery Or Alternator Problems?

One of the most common issues that can affect your car’s battery or alternator is a loose or corroded connection. If any of the connections are loose, it can cause a drop in voltage and prevent the alternator from charging the battery properly. Another common issue is a buildup of sulfate on the lead plates inside the battery, which can prevent charging and cause starting problems.

In some cases, an alternator may fail due to a manufacturing defect or simply wear out from normal use over time.

How Can You Prevent Battery Or Alternator Problems?

One of the most common questions we get here at our shop is “how can I prevent battery or alternator problems?” While there are many things that can cause these types of issues, there are a few key things you can do to help prevent them.

First, make sure you always keep your battery clean and free of corrosionThis can be done by regularly checking the terminals and cleaning them as needed. You can also use a product like Battery Tender to help keep your battery in top condition.
Second, don’t let your car sit for too long without starting it upThis can cause the battery to drain and may eventually lead to problems. If you know you won’t be driving your car for a while, hook it up to a trickle charger to keep the battery topped off
Finally, have your charging system checked regularly by a qualified mechanicThey will be able to tell if there are any potential issues and fix them before they become big problems. By following these simple tips, you can help prevent battery or alternator problems down the road.

Battery Vs Alternator Vs Starter

There are three main electrical components in most cars: the battery, alternator, and starter. Each has a specific purpose and all must work together to keep your car running smoothly. Here’s a look at what each does and how they work together:

The battery is responsible for starting the engine. It provides the initial power needed to get the engine going. Once the engine is running, the alternator takes over and produces the electricity needed to run all of the car’s electrical systems, including lights, wipers, radio, etc.

The starter is only used when starting the engine; once the engine is running, it isn’t needed. If any one of these three components fails, your car won’t run. That’s why it’s important to have them all checked regularly by a qualified mechanic.

Weak Car Battery Symptoms

If your car battery is weak, it may exhibit one or more of the following symptoms:

1. The engine cranks slowly when you try to start the car.

2. The headlights are dim, and they may flicker when idling.

3. The interior lights are dim, and they may flicker when idling.

4. Electric accessories, such as the radio or power windows, work erratically or not at all. A weak battery can often be recharged so that it works properly again.

However, if a battery is too far gone, it will need to be replaced.

Dead Battery Symptoms

A dead battery is one of the most common car problems. There are several symptoms that can indicate a battery is dying or already dead. If you experience any of the following, it’s time to replace your battery:

Dead Battery SymptomsExplanation
The engine won’t startThis is the most common symptom of a dead battery. If your battery is completely dead, you’ll need a jump start to get the engine going.
The headlights are dim or flickeringA dying battery can cause your headlights to dim or flicker. This is because the electrical current produced by the battery isn’t strong enough to power the lights properly.
The dashboard lights are dim or flickeringLike the headlights, a weak electrical current can cause the dashboard lights to dim or flicker. This can make it difficult to see while driving at night.
The car stereo cuts in and out A dying battery can also affect your car stereo, causing it to cut in and out as you’re listening to music. Again, this is due to an insufficient electrical current from the battery.

Signs of Bad Alternator

An alternator is a vital component in your car’s electrical system, and it plays an important role in keeping the battery charged. The alternator charges the battery while the engine is running, and it provides power to the car’s electrical accessories when the engine is off. If your alternator starts to fail, it can cause a number of problems.

Here are some signs that you may have a bad alternator:

1. Your Car Won’t Start

If your alternator is failing, it may not be able to provide enough power to start your car. This can be especially evident if you try to start your car after it’s been sitting for a while.

2. Your Headlights Are Dim

Headlights rely on electricity from the battery to function properly. If your alternator isn’t charging the battery correctly, the headlights will appear dimmer than usual.

3. Your Dashboard Lights Are Flickering

Just like your headlights, dashboard lights rely on electricity from the battery. If there’s something wrong with the way your alternator is charging the battery, these lights will flicker or turn off completely at times.

4. Your Car Stalls

A failing alternator can cause your car to stall unexpectedly because it’s not providing enough power to keep all of the systems running smoothly. This can be extremely dangerous if it happens while you’re driving!

Can You Jumpstart a Car With a Bad Alternator?

If your car has a bad alternator, you may be able to jumpstart it. However, this is only a temporary fix and you will need to replace the alternator as soon as possible. To jumpstart a car with a bad alternator, you will need to connect the positive terminal of your battery to the positive terminal of the other battery.

Then, connect the negative terminal of your battery to the negative terminal of the other battery. Finally, start the engine of the car with a good battery and let it run for a few minutes. Keep in mind that jumping into a car with a bad alternator is only a temporary fix.

You will need to replace the alternator as soon as possible to avoid further damage to your vehicle.

Car Not Starting But Battery is Fine

If your car won’t start but the battery is fine, it could be a number of things. It could be a problem with the starter, the alternator, a blown fuse, or a bad ignition switch. If you’re not sure what the problem is, it’s best to take it to a mechanic and have them diagnose it.

Battery Or Alternator Reddit

If your car’s battery is dead, you may be wondering if you need to replace the entire battery or just the alternator. Here’s what you need to know about replacing a car battery or alternator. If your car won’t start and you think it may be the battery, there are a few things you can do to test it.

First, check to see if the headlights are dim or flickering. If they are, it’s likely that the battery is the problem. Another way to test the battery is to try starting the car with jumper cables.

If the car starts with jumper cables, then it’s probably just the battery that needs to be replaced. However, if the car doesn’t start with jumper cables, then it could be either the battery or alternator that’s causing the problem. If you’re still not sure whether it’s the battery or alternator that needs to be replaced, take your car to a mechanic for a diagnostic test.

The mechanic will hook up a special device called a voltmeter which will tell them whether it’s the Alternator voltage regulator which isn’t working properly or if something else is wrong entirely.

How Long Does It Take for a Bad Alternator to Drain a Battery?

How long does it take for a bad alternator to drain a battery? It depends on several factors, but typically it will take a few days or weeks. The main factor is how much current the alternator is drawing from the battery.

A small draw can slowly drain a battery over time, while a large draw can quickly discharge it. Other factors include the age and condition of the battery, as well as ambient temperature. If you think your alternator might be going bad, have it checked by a qualified mechanic as soon as possible to prevent any damage to your car’s electrical system.

Conclusion


It could be a problem with the battery, the starter, or the alternator. If you’re not sure which one it is, here’s how to tell. If the problem is with the battery, you’ll likely see signs like slow cranking when you try to start the car, dim lights, and electrical problems.

If it’s an alternator issue, on the other hand, you might notice that your car is running poorly or that the lights are flickering. In either case, it’s best to take your car to a mechanic so they can diagnose and fix the problem.

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