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Can You Jumpstart a Car with a Bad Alternator: 90% Don’t Know

The main job of an alternator is to replenish the car’s battery by converting chemical energy into electrical energy. But how do you deal with a car’s faulty alternator? Can you jumpstart a car with a bad alternator?

The good news is that a car can run on its own until its battery gets out of charge. However, it would be best to avoid driving a car with a faulty alternator. Your car engine may stall as the car battery doesn’t receive charge due to a faulty alternator. There may be many other electrical issues due to a failing alternator.

As the alternator fails to assist the battery, even the jumpstart battery will drain fast. Once you remove the jumper cable, the engine will not stop instantly. Once the battery voltage goes considerably low and unable to source any electrical component in the car, the car will stop.

Symptoms of a Bad Alternator

The alternator is an essential component of a car’s electrical system. It converts the mechanical energy from the engine’s rotation into electrical energy to charge the battery and power the vehicle’s electrical systems. A bad alternator can cause various problems for a car, ranging from dimming lights to complete electrical failure. Here are some of the symptoms of a bad alternator:

How to Identify a Bad Alternator?

The easiest way to identify a bad alternator is to check the warning lights on the dashboard. If the battery light comes on while driving, it could indicate a bad alternator. Additionally, if the car’s headlights or interior lights are dimming or flickering, it could indicate that the alternator is not charging the battery correctly. A simple way to test if the alternator is working correctly is to use a multimeter to check the voltage output. A good alternator should output around 14 volts when the engine is running.

Warning Signs of a Bad Alternator

Other warning signs of a bad alternator include strange noises, such as grinding or whining, coming from the alternator. Burning smells or smoke coming from the alternator or the engine compartment could also indicate a problem. Furthermore, if the car’s electrical systems start malfunctioning, such as the radio or air conditioning, it could be a sign of a bad alternator.

Common Symptoms of a Bad Alternator

Some common symptoms of a bad alternator include difficulty starting the car, even with a fully charged battery. This is because the alternator is not providing enough power to start the engine. Additionally, a bad alternator can cause the battery to drain quickly, even when the car is not in use. This can result in the car stalling or shutting off while driving.

Can You Jumpstart a Car with a Bad Alternator?

Jumpstarting a car is a common solution to start a vehicle with a dead battery. However, if the alternator is bad, jumpstarting the car may not work correctly. Here is what you need to know about jumpstarting a car with a bad alternator:

Explanation of Jumpstarting a Car

Jumpstarting a car is the process of using another car’s battery to start a vehicle with a dead battery. This is done by connecting jumper cables from the functioning battery to the dead battery, allowing the functioning battery to provide enough power to start the engine.

Possibility of Jumpstarting a Car with a Bad Alternator

Jumpstarting a car with a bad alternator is possible, but it may not work correctly. The functioning battery can provide enough power to start the engine, but the car may stall or shut off shortly after starting. This is because the alternator is not charging the battery, and the car is running on the battery’s power alone. Once the battery’s power is drained, the car will shut off.

What Are the Risks of Driving a Car with a Bad Alternator?

It’s not a good idea to drive around with a damaged alternator. They can cause problems with your car’s electrical systems, making it more difficult to start the engine and drain the battery, rendering it completely unresponsive.

1. Car Battery Damaged Due to Overcharging Leading to Replacement Cost

A defective alternator with a damaged regulator could cause your car’s batteries to overcharge. If your car’s electrical system has not been checked thoroughly, it may take several battery replacements to realize that the alternator is causing them damage.

2. Unable to Start Because the Battery failed to Charge

When they fail, some alternators can’t generate enough dc voltage to charge your battery. The result is a partially charged car battery that doesn’t have enough power to turn it on.

Alternators that are defective or have short circuits inside can cause your car to stop starting.

3. Car Losing Power Suddenly While Driving

Accidentally, your car could lose power and cause it to stop. Both the alternator and the battery in the car cannot provide enough power to the electrical system.

4. Unreliable Performance

An alternator that charges intermittently can cause problems for your car’s battery. The alternator charges the battery, and the car starts. It stops if the alternator fails.

Does Jumping Start a Car With Bad Alternator Damage The Battery?

A dead battery is scary, but a failed alternator could be scariest. Jumpstarting a car using a defective alternator won’t harm the battery if done correctly. But, if the bad alternator overcharges the battery, it may lead to high voltage leading to premature cell. There may be a factor in how much the alternator fails. But even if there is a dead battery, you can jumpstart the car using an alternator.

When the alternators develop a dead short circuit at both power and ground, they could draw large loads, which can cause damage. But that’s unlikely. Your main concern should be whether or not your car is running without an engine.

After you disconnect the cable, this may stop running quickly and easily. It would help if you recharged the batteries to run out of the stored electricity. Battery power is required to run the ignition system, ECU, running fuel pump, and injectors.

How to Jump-Start a Car With a Bad Alternator?

You can jumpstart your vehicle if the alternator stops working. However, you will need to get a new alternator ASAP. Follows the instruction below to get the insight:

Preparing for Jumpstart:

  • Separate both the cars so that they do not touch each other, and take out the ignition keys for both the donor and receiver vehicles
  • Locate the negative (BLACK) and positive (RED) wired on the battery. Clamps should not touch anything at this point.

Look for a Donor Car With a Good Battery.

Without a fully charged donor car option, you can’t jumpstart dead batteries. It would be best if you had someone to jumpstart your battery. However, ensure that the battery you are using has a full charge. The procedure will not work if yours isn’t prepared.

Let The Engine Running

You should run the engine for at least 3-4 minutes before the jumpstart. You will need to connect the jumper cables before you start the jumpstart. Your car should also be turned off. However, you can optimize the process by ensuring that the other vehicle has been fully primed.

Turn Accessories off

Turn off all car’s electronic accessories in your car (air conditioner, heater, radios, chargers, GPS, and phone chargers). So you can save all your battery power. Your car must be able to engage its fuel injectors and computer system.

The jumpstart will not work in any less sunny weather. Windshield wipers or headlights can drain too much battery power. Once everything is in order, you can begin the jumpstart.

Take It to The Mechanic.

If your venture is successful, you should immediately drive to a mechanic. Not all shops are within your reach, so you may not have the time to drive there in 5 minutes. Towing services will be required if they’re too far away. Avoid driving on major interstates or highways.

To maximize efficiency, you should drive slowly.

Use a Jumper Pack

Jumper packs can supplement other jumpstarts or as a standalone device. Jumper packs are a portable jumper system that charges your vehicle’s battery by itself. You can store it easily and make sure your battery is protected.

Factors that May Affect the Success of Jumpstarting a Car with a Bad Alternator

Several factors can affect the success of jumpstarting a car with a bad alternator. The age and condition of the battery play a significant role. If the battery is old or in poor condition, it may not hold a charge for very long, even with a functioning alternator. Additionally, the temperature can affect the battery’s performance, as cold weather can reduce the battery’s power output. The type of vehicle and its electrical system also play a role, as some cars have more demanding electrical systems that require a functioning alternator to operate correctly.

A bad alternator can cause various problems for a car’s electrical system. If you suspect a bad alternator, it is best to have it checked and replaced by a professional mechanic. Jumpstarting a car with a bad alternator is possible, but it may not work

How Long Can I Drive with a Bad Alternator?

Depending on the condition of the faulty bearing, the distance travelled with a bad alternator varies. You can easily drive for a few weeks if the faulty bearing is at its early stage. If the faulty bearing has reached an advanced stage, it will not allow you to drive.

Never run your car when the faulty bearing is advanced, as you have already overstretched your driving limits. Pushing it further will lead to smoking, overheating, and permanent damage to th alternator.

Frequently Asked Questions

How Can You Tell if it’s Your Alternator or Your Battery?

A problem with your battery or alternator could be that your car is not charging. Your alternator may be defective if your car’s battery can start but then dies while it runs. It’s possible that your battery is not charging and your car won’t start.

Can I Drive a Car with a Bad Alternator?

An alternator failure can cause a car to stop running for a limited time. When the engine is running, the alternator charges the battery. Once the battery is gone, the vehicle will stop working and die.

Can I start a Car Without an Alternator?

The car will continue to run until it runs out. What is the life expectancy of a car without an alternator? It all depends on how big the car’s battery is. The vehicle might not start if the battery is fully charged.

Can a Bad Alternator Drain the Battery When the Car is Turned Off?

The alternator cannot recharge the battery when the engine is turned off. This allows little electrical mishaps to drain your battery completely. A parasitic draw is a term that describes the battery strain caused when there are no electrical whoopsies.


Driving with a bad alternator only works when the alternator is not severely damaged or broken. In such cases, the car will not start. However, the car will start without issues once the alternator is fixed. There are several ways to fix this issue. Some people use a jump-starter, a small tool that helps jumpstart a dead car.

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My Name is Christopher Angels, and I am a postgraduate in mechanical engineering. Cars have always excited me as a child, and soon I decided to dive into the world of cars by pursuing mechanical engineering. I also worked as a Mechanic for over 3 years to understand Cars' anatomy and how each part contributes to its working.

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