Can You Jumpstart a Car with a Bad Alternator? [+ Replacement Cost]

Can you jumpstart a car with a bad alternator? Well, circumstances may require that you find a way to still drive with a bad alternator. 

But even if you can jumpstart a car with a bad alternator, how far can you go with the car? Is it advisable to do this? What’s the replacement cost of a bad alternator? These issues and more are addressed in this article. Read on!

A car alternator refers to a type of electrical generator designed to charge the battery in automobiles and also serves as the powerhouse to the electrical system of the car’s engine while it’s running.

Typically, there are two power sources for modern automobiles. These are mechanical and electrical power sources. These two power sources for the vehicle work closely together to provide the needed power to keep the vehicle fully functional.

The car’s engine once ignited begins to generate mechanical force to power the mechanical components of the car. The battery and the alternator are responsible for supplying power to the electrical components of the car.

See what happens: once you ignite the engine using the battery, the alternator converts the mechanical energy from the engine to electrical to keep the battery continuously charged so it can keep powering the electrical components without running down.

But sometimes, you see the battery removed from a vehicle with its engine still running and with the electrical system still working perfectly.

Well, that’s because of the car’s alternator.

Of course, you know if you put off the car, you just can’t start it again without it.

So, this is how the battery and the alternator work. When it comes to the electrical system of any vehicle, the alternator plays a very important role. The moment it develops a problem and stops working as it should, it opens the vehicle to an array of problems. 

This article, apart from answering the question, “can you jumpstart a car with a bad alternator?” It will also look at the symptoms of a bad alternator.

Can You Jumpstart a Car with a Bad Alternator

Signs and symptoms of a bad alternator

Unusual noises from the belt

Unusual noise coming from the belt may not be directly associated with the alternator but since the belt that links the alternator to the engine for mechanical energy has gone bad, it automatically affects the alternator’s performance.

The car’s belt may have become worn or misaligned, hence, causing a squeaking sound that can be heard from the hood.

The alternator on the flip side is designed to work in tandem with the speed of the belt. 

Also, the alternator’s bearings may have become pitted and worn and end up producing unusual sound. As the bearings keep getting worse, you may not be able to bear the sounds coming from there.

Difficulty starting the car

When it comes to difficulty starting a car, two components would most likely be the culprit: the battery and/or alternator.

One way to test these components is to replace the battery. If the new battery gets drained shortly than normal, it means the alternator has not been charging it—meaning the alternator is in a bad shape.

But if the new battery works without more problems, that means the old battery was the problem.

You may be wondering what went wrong with a battery that you thought was healthy and has been working. Well, you may have forgotten to switch off your lights and that drained the battery.

However, if there’s no extra battery to run this test, try to jumpstart the car. The process of how to jumpstart a car is covered in this article.

Jumpstarting the car would help it charge the battery fast, maybe just enough to help you locate the nearest mechanic shop.

If your engine continues running after jumpstarting and putting back the battery that was originally in the car and then once you turn off the car you can’t start it again, it means your battery can’t retain charges again.

Electrical problems

Another symptom of a faulty alternator is the occurrence of electrical problems. The electrical problems here arise because the electrical system that is controlled by the alternator and battery can’t supply enough power needed to run it.

Your car radio may suddenly go off or your headlights go dimer. You may also notice the lights fluctuating.

Engine stalling

Experiencing your car engine stalling may signal that your alternator is bad. When the alternator begins to fail, even while the car is running it may not be charging the battery or it may be charging it poorly. 

As a result, there may not be enough power to keep the car running smoothly resulting in the engine stalling.

Engine stalling may also be due to the idle control valve, which can’t keep the throttle plate open so the car can get enough air. Usually, the idle control valve problem happens when you lift your foot from the gas pedal and go to the break.

A car can also stall because of the fuel injector, which isn’t getting electricity to function properly.

Can you jumpstart a car with a bad alternator? 

Even though it’s not encouraged, the answer is yes.

You can still jumpstart a car with a bad alternator. However, once it’s done you should take the car in for a replacement of the defective alternator.

This is because the car would fully depend on the battery for all its electrical needs even when the battery isn’t charging.

So, if you don’t find a solution to the situation after jumpstarting the car, once the battery runs down, the engine shuts down and that’s going to be a double problem—faulty alternator and drained battery.

Once the alternator fails and the car is jumpstarted, try as much as you can to reduce the load on the battery so it doesn’t run down quickly.

The best option that you should take at this time is to locate the nearest auto repair shop for a replacement.

A 12 Volt car battery may run down faster than you can imagine because what usually keeps it going has just become defective.

Apart from you trying to reduce the load on the battery by turning off your heater or disconnecting your phone from the charger, the battery still has critical components to power such as the power steering, fuel pump, fuel injector, onboard computer, etc. which consume a lot of power.

Are there dangers of jumpstarting a car with a bad alternator? 

The only concern with jumpstarting a car is that it should be done correctly.

As long as you can do it correctly, both the donor and the recipient’s car remain safe. There’s more risk with driving a car with a defective alternator than there is in jumpstarting it.

As earlier said, a bad alternator can result in an array of problems within the car’s electrical system.

How much does it cost to replace an alternator? 

The cost of replacing an alternator varies from vehicle to vehicle. The cost would largely depend on the year, model, and make of your vehicle.

Typically, a new alternator costs between $200-$700 including labor charges.

However, if there are accompanying problems as a result of the faulty alternator, you will have to pay more.

For example, you may end up with more electrical problems because of your poor handling of the problem when you first noticed it or ignorant of the fact that you were having an alternator problem so you had to keep troubling the car when you ought to have stopped using it.

Also, you may end up changing the battery if you allow it to become drained and it can’t work again.

Take note that your insurance may not cover a problem with your alternator except the problem with the device is due to an accident.

On the flip side, if your insurance policy covers roadside assistance, you can call your insurance company for help, after all, you got stranded by the roadside because of a bad alternator.

How far can you drive with a bad alternator?

How far you can go with a bad alternator depends on many factors.

  • If the faulty alternator still has a little life in it, that can help.
  • How far you can go with a bad alternator largely depends on the strength of your battery after jumpstarting the car.
  • The speed at which you drive matters. It is advisable you don’t speed up.
  • The electrical load on the car. You should try to shut down electrical devices as much as you can. This includes the heater, lighting, phone charging, radio, etc.
  • The age of your car. Old cars tend to consume more power.
Can You Jumpstart a Car with a Bad Alternator

How to jumpstart a car with a bad alternator

Jumpstarting a car with a bad alternator has a few things to consider when compared with the process of jumpstarting a car the conventional way.

Understanding that you will have to drive the car to a mechanic shop, you should allow the car’s battery to charge for at least 15 minutes before disconnecting and starting your car.

The following steps can help you jumpstart a car with a bad alternator.

It is divided into five sections.

Getting started

  1. Separate the two cars in a manner that they don’t touch each other.
  2. For both vehicles, the keys must not be on the ignition.
  3. Identify the battery terminals based on their polarity.
  4. Keep the clamps separated from each other.
Can You Jumpstart a Car with a Bad Alternator

Connect jumper cables

  1. Attach one RED end of the clamp to the RED/POSITIVE terminal of the good battery from the donor car.
  2. Attach the RED end of the clamp to the RED/POSITIVE terminal of the bad battery of the recipient car.
  3. Attach one BLACK end of the clamp to the negative terminal of the good battery while the other end gets grounded. To ground it properly, attach it to an unpainted frame, bolt head, bracket, nut, or stud of the car that needs help.


(1) Make sure the jumper cables are connected firmly to the batteries.

(2) The battery of the vehicle that’s feeding you must be in good health and fully charged. This is necessary because your battery is going to draw a greater amount of energy in the jumpstarting process.

Start the car 

  1. Start the donor car i.e., the car with a good battery.
  2. Let it run for 3-4 minutes at 2000 RPM.
  3. Allow it to run for up to 15 minutes if you intend to drive with the bad alternator.
  4. After waiting for the donor car to run for 3-4 minutes, try to start the one with the bad alternator and dead battery. If the car attempts to start but won’t, try starting it again after another 3-4 minutes.

Disconnect the clamps 

  1. Get the BLACK/NEGATIVE clamp off the dead battery.
  2. Get the RED/POSITIVE clamp off the dead battery.
  3. Get the RED/POSITIVE clamp off the good battery.
  4. Get the BLACK/NEGATIVE clamp off the body of the recipient’s car where it was grounded.

Don’t waste any time immediately when the clamps are disconnected since you’ll be driving on reserved power. However, don’t drive too fast. Get to any nearest auto repair shop within 5-7 minutes.

Note that this is a temporary solution. In the absence of a working alternator, you can’t go far with your battery.

Having the car towed to a mechanic shop can also be a good option if you can afford the cost of a towing van.

Turn off accessories

You need every energy that you can grab from your battery to get to the nearest auto repair shop.

Thus, turn off all electrical devices such as phone charger, radio, GPS, CD player, air conditioning, and heater.

The little reserved energy should be allowed to go to the critical components of the car such as the fuel pump, fuel injectors, onboard computer, water pump, and power steering.


(1) Avoid traffic-congested areas.

(2) If you are doing this in the night that you’d need to turn on your headlights, or during the rain where you need your wiper to be working, the battery may drain out fast.

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