Can You Jumpstart a Car With a Bad Alternator?

Getting into your car and turning the key only to find that your car won’t start is a stressful situation. You use your car to get to work, school, home, and everywhere else, so not having it working properly can be a hassle. However, if you find that your battery is dead, there may be an issue with the alternator that caused it to die. 

Even if your battery is dead and your alternator isn’t working correctly, you can jumpstart your car to be able to get home or to a repair shop. Just because the alternator won’t continue to charge your car’s battery once the vehicle is running doesn’t mean that it can’t be started at all.

With a little jumpstart, you will be able to get to where you need to go!

However, knowing how to do it properly will keep you from making a mistake and causing more problems. Dealing with electricity can cause damage or injury if you misuse the cables, so you want to ensure that you are being safe while you are jumpstarting your vehicle.

This article will go over what an alternator is, what it does, and all that you need to know about how to jumpstart your vehicle when yours in not working. 

What is an Alternator? 

An alternator is an important part of any vehicle’s engine because it is a power generator for electricity and charges the car battery as you are driving so that you maintain power.

Most cars, except a small number of hybrid vehicles, have one in their engine. This mechanism is bolted to the engine of the car with a serpentine belt, also called a drive belt. 

An alternator charges the car’s battery, but also gives electrical power to other systems throughout the vehicle.

The lights inside your vehicle will likely not work very well, or at all if you jumpstart your car and drive it without full battery power. This is because the alternator also supplies the electrical power to the lights.

This unit typically does not need any maintenance but may need to be replaced once it fails. However, this is something that should not occur for ten to fifteen years, depending on how much you drive.

Even when your alternator fails, because your battery is at full power, you will still be able to drive your vehicle for a short time on the battery power alone.

How To Tell If You Need a New Alternator 

Once your vehicle hits the ten-year mark, you might want to look out for a few signs that your alternator may be failing before your vehicle stops completely.

Here are the most common signs to look for when you believe that your alternator may be in need of repair or replacement.

Sign #1 – Lights Dim When Idling 

If you start to see that the lights on your dashboard begin to dim when your car is idling, this could be a sign that your vehicle is not getting the full amount of power that it should from the alternator.

You will also see that the lights will get much brighter whenever you rev your engine. This could be a sign of several issues related to the battery power, so it doesn’t mean that the alternator is bad, but it could be a cause.

Sign #2 -A Loud Buzzing Sound 

If you start hearing a buzzing sound and it is coming from the area near the alternator, then it could be a loose bearing.

Some cars might have a pulley system that holds the alternator, so in those vehicles, a bad pulley could be the issue. 

Sign #3 -The Battery Light Comes On 

The light on your dashboard that is shaped like a battery is meant to tell you that something is wrong with the power.

This could mean several things, but one of the causes could be that the alternator is failing.

If the battery is not getting any more power and is running on the power it has left, then the light will come on to alert you.

How to Jumpstart Your Car With a Bad Alternator 

If you have checked your engine and found that the alternator is indeed the problem, then you still have the option to jumpstart your car to get it to a repair shop.

Jumpstarting your car is fairly easy, even if you have never done it before, and following the steps below will show you how to do it so you can get back on the road!

Step 1: Get another car to hook up to 

You need another vehicle to connect your battery to in order to get your car jumpstarted. If you are at home, then calling a neighbor or friend over to help will be easy.

However, if you are on the side of the road, then you may need to flag down a vehicle that is willing to stop and help you out. 

Step 2: Check to ensure that your car is off 

Once you have someone willing to help out, you will want to check to make sure that your vehicle is turned off before beginning to connect about cables.

If not, you could make sparks that could be a fire hazard, or even damage your vehicle. So, turn it off and take the keys with you. You will also want to check that the person helping you has shut their car off as well. 

Step 3: Attach the red (positive) cable  

When you are ready to connect the jumper cables, you will start with the red cable and attach it to the positive terminal on your vehicle.

Then, take the other end of that same cable and attach it to the positive terminal situated on the other person’s vehicle.

Editor’s Note: Jumper cables are an essential item to carry in every car. If you don’t already have a set, here is a fantastic (and affordable) pair.

Step 4: Attach the black (negative) cable 

After you correctly attached the red cable, you will take the black cable and attach it to the negative terminal that is on the car with a properly working alternator.

Then, take the opposite end of the cable and attach it to the engine as a ground. You can attach the cable anywhere there is no chrome or paint. You shouldn’t ever attach this cable to the battery itself.

Step 5: Start the other person’s car

By starting their working vehicle, this will allow the battery to be charged off of that car’s electrical power system. You should let the car run with the cables attached for around five minutes to allow the battery on your car to be charged enough to start. 

You can test your car after a few minutes of charging to see if it will start. If it doesn’t turn on yet, then keep the other car running with the cables attached until your vehicle has enough power to start the engine. 

Step 6: Detach the cables 

Once your car has started, you can begin to remove the cables starting with the black one first. Remove the cable from the other person’s car, then remove the red cable from your car. Then, you can remove the black cable end from your car, and detach the red cable end of the other car. 

You need to keep the cable ends apart even when one side is off, and when both ends are detached, you can begin to put them away. 

Step 7: Head to a repair shop immediately!

Once your car has started, you will need to head straight to the nearest body shop for repairs. With a failing alternator, you will not have lights, which can be very dangerous. Also, if you continue driving it when the sun goes down, you could get a ticket. 

So, go to your local repair shop and get the problem looked at and fixed so that you will not have to jumpstart your vehicle again. 

Tips for Getting a Jumpstart

If you are having trouble keeping the cables apart as you are detaching them from the vehicles, there is a way to make it easier!

Take a piece of cardboard that is not conductive and attach the removed cables to it. This will let you focus on taking off the proper cables in order, rather than dealing with keeping the cables from touching. 

If your car has stopped at night, then you will need lights as soon as your car starts up. This will be difficult to get because the battery will need to sit for a long time.

Having a friend or family member to call instead of waiting for another driver to stop and help will be your best bet. That person will have to sit and wait with you while the battery charges, which could take some time. 

However, if you don’t want to wait around, then you should just call a tow truck to take you to the repair shop.

They might cost quite a bit of money, but it is better than having to wait for an hour while your car battery charges, or getting a ticket if you don’t have your lights on after a quick jumpstart. 

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Hi, I'm the founder of! Having owned a wide variety of vehicles in my life, I was astounded at how hard it can be to find answers to common automotive questions. Rather than sit idly, I decided to create this website to help others!