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Can You Jumpstart A Car With A Bad Alternator? [ Answered 2022 ]

Can You Jumpstart A Car With A Bad Alternator? [ Answered 2022 ]

As a car owner, you know how crucial your alternator is to keep the vehicle’s battery charged. As a result, all the components in your car can draw the necessary power to function properly.

Have you wondered whether you can jumpstart your car in case the alternator goes bad? Of course, you would try to get the jumpstart issue sorted at the earliest. However, if you are unable to get the faulty alternator fixed at the moment, can you jumpstart your car?

We have explained whether or not you can jumpstart your vehicle using a malfunctioning alternator in this article.

Can you jumpstart a car with a bad alternator?

Yes, it is possible to use a bad alternator to jumpstart your car. This way, your vehicle would keep running for some time. You can start your vehicle if the battery is in good condition, regardless of how poor the alternator turns out to be.

The reason is, the battery would be completely supporting the power requirements of the car in case the alternator fails to deliver the necessary voltage.

Even though a bad alternator can help you jumpstart your car, experts recommend not to do so. Only if you decide to drive for a short distance, this might turn out to be a necessity. You need to jumpstart a car so that the flat battery starts running. So, when you jumpstart the car, the battery might already be very low.

Now, the alternator wouldn’t provide any kind of assistance to the battery. This battery would go flat much faster than it would do when you charge it properly. Moreover, if you have a high electrical load in your car like a phone charging, you would get a flat battery even faster.

So, when you do away with the jumper cables, the engine wouldn’t stop immediately. The car would run so long that the voltage of the battery doesn’t dip excessively low. Ultimately, when it does, the electrical systems would not be functioning.

How To Jumpstart A Car With A Bad Alternator?

Even if you have a bad alternator, the process of jumpstarting your car would be the same as what you do with a properly functional alternator. However, you should know the exact process that involves a few tricks.

In these situations, you need to keep the cables connected for at least three minutes. Now, if you need to drive after jump starting the car, make sure to charge it for 15 minutes at least.

Otherwise, you should expect the battery to drain out faster. With the malfunctioning alternator no longer supplying an adequate voltage to the car, you might face certain dangers while driving.

What you should do before you jumpstart a vehicle

  • You would need the battery of another car to jumpstart your vehicle. So, take care that there is no contact between the two cars.
  • Take away the keys from the ignition.
  • On the battery locate the negative and positive wires.
  • Make sure that the clamps do not come in contact with each other during the process.

Attach the clamps

  • Establish a connection between the dead battery and the positive clamp.
  • Attach the good battery to the other positive clamp.
  • Now attach the good battery to the black clamp.
  • Establish a connection with the other negative clamp and a bare metal lime bolt head, nut, or stud.

 Start your engine

  • Now use the good battery to make the engine start
  • At 2K RPM, run the car for 3 minutes
  • If you want to use the bad alternator while driving the car, run it for 15 minutes at the same RPM
  • You may have to run the engine longer in case the outside is cold
  • Try to use the bad alternator to crank your car
  • Try for another few minutes if the car doesn’t crank

 Do away with the clamps

  • First, do away with the black clamp that you had attached to the dead battery
  • Now remove the red claim from the same battery
  • Next, put aside the positive claim on the good battery
  • Lastly, you need to remove the negative clamp that you attached to the good battery


When you try to jumpstart your car using a bad alternator, make sure to put all the accessories off. These include the AC, heating, CD players, radio, phone charger, GPS, and other components that might rob the batter of its power. You would like to conserve maximum power, so that you can easily jumpstart your car with a faulty alternator.

Try to carry out this process when it’s dry outside during the daytime. This ensures that you won’t need your windshield wipers or headlights, which would help you conserve the power in your battery. Once you manage to jumpstart your car using a bad alternator, try to visit the mechanic at the earliest and get the alternator fixed.

How do I charge my car battery with a bad alternator?

If you have a malfunctioning alternator, you can charge the battery of your car through the following steps.

Step 1

In the first place, you need to jumpstart your car. In case the battery is dead, use jumper cables to provide charge temporarily to the battery. Now attach the cables to the vehicle when the engine is running, and then to the car’s battery.

The cables should remain attached for a long time (several minutes). During this time, the driver needs to park the vehicle and press the accelerator. As a result, the battery would have a surge in electricity. Now disconnect the cables once you start your car.

Step 2

Get a portable battery charger for your car and connect it to your battery. Completely charge the charger and establish a connection between your battery’s positive terminal and the red clip.

Connect the negative terminal to the black clip. The strength of your charger broadly determines the time that the battery would take to receive a full charge.

So, if you have a 10-amp charger, you can expect the battery to completely charge in 45 minutes. To get an idea about the specific time, you need to check out the manual of your charger.

Step 3

Establish a connection between a wall charger and your car’s battery. This would work in case you don’t have a portable charger. In case it’s dry outside, you can also get an extension cord to get your battery charged while it remains in the car.

You can also get the battery removed. Now pull the battery out and take it to the charger. Take care that there is an even surface when the charging takes place.

Establish a connection between the negative terminal and the black clamp, while the positive terminal remains connected to the red clamp. You would notice the LED light turning green on the charger when you fully charge the battery.

How long will a car run with a bad alternator?

This largely depends on several factors, including the state of the car battery, the condition of the alternator, the overall electrical load in your vehicle, speed, and the age of the car.

So, when you try to run your car with a bad alternator, it would run around 13 to 15 miles. Roughly, you can travel for 20 minutes after you jumpstart your car. However, you can extend this distance if you manage to retain a low RPM and refrain from speeding.

In case you jumpstart your car with a bad alternator while on a low battery, you should expect it to travel for 7 to 10 miles. This should be equivalent to 10 minutes of driving time.

Disadvantages of Jumpstarting A Car With A Bad Alternator

With the appropriate process, neither the car of the donor nor the recipient would sustain any damage. The process would be safe, but mechanics don’t recommend this method to jumpstart your car. When you drive a new car with a bad alternator, you cannot put aside the risk altogether.

The alternator supplies power to all the electrical components in your car.

So, when you start your car’s engine, the battery needs to receive a full charge to ensure the proper functions of all these components. Therefore, the manufacturers design most alternators to generate around 14.5-volts in case you have a 12-volt system.

The functioning of most of the components of your car largely depends on the alternator. Particularly, new cars remain susceptible to the danger of a component failure, as they wouldn’t prefer low voltages. Therefore, the potential dangers of jumpstarting your car with a bad alternator include the following.

1. Problems with electric water pumps

The electric water pumps effectively pump the water from the car’s radiator. This water helps the car to run smoothly, as it moves through the motor. In case the car keeps going even after the water pump fails, you might encounter overheating issues leading to permanent damage in the engine.

2. Issues with the power steering

In some vehicles, the power steering works on electricity. Without adequate power in the steering pump, you might find it problematic to steer the vehicle. This eventually exposes the car to the risk of accidents, as you wouldn’t be able to maneuver the vehicle properly.

3. Fuel pump problems:

The function of the fuel pump is to supply the engine of your car with power. Even old vehicles have fuel pumps that run on electricity. So, when the lack of power prevents the fuel pump from providing adequate fuel to the engine of your car, it would simply stop operating.


Jumpstarting your car can land up in an awkward scenario, as the vehicle might shut off even if it doesn’t sustain any real damage. So, it would be wiser to tow your car to the mechanics rather than trying to jumpstart it using a bad alternator.

Therefore, technically you can jumpstart your car even if the alternator is not working. However, you would be wise not to do so as you can end up with some kind of component failure in your vehicle.