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Can You Jumpstart a Car With a Bad Alternator?

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Since your car battery relies on the alternator to maintain its charge, it becomes low when the alternator goes bad. Unfortunately, you cannot start your vehicle with a low battery and a faulty alternator. But if you cannot start the car, can you jumpstart it? Let us find out.

Can you jumpstart a car with a bad alternator?

You can jumpstart a car with a bad alternator. For vehicles to start, they require just enough electricity to run critical components. So, as long as the battery in your car is in good condition and the jumper provides enough electricity, your vehicle can come to life.

There’s more you should know about jumpstarting a car with a bad alternator. So, in this article, we describe how to jumpstart a car and answer some questions about jumpstarting a car.

Can You Jumpstart a Car With a Bad Alternator?

Ordinarily, when your alternator is not in good condition, your car battery will not retain power. As expected, if your battery does not hold its charge, it will become low. Sadly, your car will not start with your alternator out of order and your battery low.

Fortunately, you can jumpstart your car even with the bad alternator. As long as your car battery is good, it can get a boost from a jumper pack or a charged battery in another vehicle.

If the boost is sufficient, your car will start. Otherwise, your situation will remain the same until you get a jumper with enough power.

For your car to start, it needs just enough electricity to power its vital components. Provide this, and it will come to life, even with a faulty alternator.

Note that jumpstarting your car is not ideal. So, you should only jumpstart your vehicle when necessary.

How to Jumpstart a Car With a Bad Alternator

You can jumpstart your vehicle in 5 simple steps:

Before You Jumpstart the Car

Before you jumpstart the car, ensure you do the following:

  • Keep the cars separated; you do not want the two cars touching each other when you jumpstart them.
  • Turn both cars off and get the keys out of the ignition. If using a jumper pack, ensure it is off.
  • Whether you are jumpstarting with a jumper pack or another vehicle, ensure the jumpstarting battery is fully charged. Jumpstarting another car draws more power than usual. So, the jumpstarting battery must hold enough charge.
  • Ensure the vehicles are far from anything flammable.
  • Identify the positive and negative terminals on the batteries. The positive terminal is typically represented by +, P, or POS. The negative terminal should have either N, -, or NEG.
  • Never let the negative and positive clamps touch each other throughout the process.

Connecting the Jumper Cables

car electric jumper used to charge dead battery

Once you have everything set as described above, connect the jumper cables following these steps:

  • Attach one of the red clamps to the positive terminal of your car’s battery. Then attach the other red clamp to the positive terminal of the charged battery in the other vehicle.
  • Attach one of the black clamps to the negative termial of the charged battery in the other vehicle. Then attach the other black clamp to a bare/unpainted metal in your car’s engine bay. It could be a stud, bolt head, nut, or the bay’s frame. The attachment to the engine bay will serve as ground.

Turn On the Jumper Pack or Car


With the jumper cables correctly connected, do the following:

  • Ask the owner of the other car to start their vehicle while yours remains off.
  • After running the car for about 4 minutes at 2000 rpm, try starting your own vehicle. (If the weather is cold, run the car for more than 4 minutes.)
  • If your car cranks but does not start, wait for 3 minutes. Then try again.
  • If the connections are well in place, but your car does not start after 5 attempts, your battery may be faulty. You may need to get a replacement.
  • Once your car starts, switch off the other vehicle, and remove the clamps.
  • Disconnect the black clamp on your engine bay.
  • Then disconnect the red clamp on your car’s battery.
  • Next, disconnect the red clamp from the battery in the other vehicle. Then, remove the black clamp from this same battery.

Jumper Pack

  • The steps are basically the same if jumpstarting with a jumper pack. But you don’t have to wait for 4 minutes before trying to start your car the first time.
  • Also, once your car starts, switch the jumper pack off. Then remove the clamps.
  • Disconnect the black clamps before the red ones.

At any point, if you are trying to adjust the connections, switch the vehicles or jumper pack off first.

Switch Off Non-Essential Accessories

A jumpstarted battery in a car with a bad alternator will not hold a charge for long. So, after jumpstarting your vehicle, ensure you switch off non-essential accessories. This way, the battery can take you a little further before it runs out of juice again.

Accessories such as GPS, heating, radio, air conditioning, and phone charging should be off after jumpstarting your battery.

Get the Car to a Mechanic to Fix the Alternator

two mechanics fixing the alternator of a car

Get the car to a mechanic to fix the alternator as soon as possible after jumpstarting it.

Do not wait for another time to fix the alternator. If you do, the alternator may become problematic; other car components may become faulty.

Also, do not hesitate in your decision to get the car to a mechanic. A jumpstarted battery will not last very long. If you waste time, the car may go off before you can get to a mechanic.

For your safety, do not get the jumpstarted car on a highway. Drive to the mechanic through local streets.

How Far Can You Go With a Car That Has a Bad Alternator?

Various factors determine how far a jumpstarted car with a bad alternator can go. So, there is no definite answer to this question.

Some of the factors that can determine how far a jumpstarted car with a bad alternator can go include:

  • The battery levels
  • The age of the car
  • The speed at which you are driving
  • The state of the alternator
  • The electrical load

Jump-started cars will not go far with lower battery levels and elevated electrical load. Also, if you drive at high speeds, your vehicle is old, or your alternator is badly damaged, the jumpstarted car will not go far.

Generally, you should not expect your car to go longer than 5 to 10 miles after jumpstarting it.

However, if you drive slowly and minimize your electrical load, you might be able to drive for up to 15 miles.

Dangers of Jumpstarting a Car With a Bad Alternator

Alternators provide electricity that powers every electrical component in your car. They typically put out a voltage that is 1.5 to 2 volts higher than the voltage of a car battery. So, if your car battery offers 12 volts, the alternator will give off 13.5 to 14 volts.

Ordinarily, the voltage produced by the alternator powers the electrical components of your car. But with a faulty alternator and low/jump-started battery, the voltage reaching the electrical parts of the car will be much lower than usual.

Some car components (especially those in new cars) do not tolerate low voltage. So, with the alternator faulty and the output voltage dwindling, the said components may fail.

  1. For instance, if your fuel pump gets low voltage, it will not pump fuel to your engine. Consequently, your car will stop.
  2. In some vehicles, the power steering runs on electricity. But with low voltage, the power steering pump may lose function. Consequently, the car becomes harder to steer.
  3. Electric water pumps may not work well with low voltage. If the electric water pumps do not work, water circulation to and from the radiator may stop. Consequently, the car may overheat, and the engine may go bad permanently.
  4. The car may switch off before any of the instances above happen. But this is also undesirable because it may mean that your vehicle will go off almost immediately after jumpstarting it. If you experience this, get a tow truck to move your car; don’t bother trying to jumpstart the car again.

Final Take

You can jumpstart a car with a bad alternator. As long as your car battery still works and the jumper battery has enough charge, you can start your vehicle. However, a jumpstarted car will not travel far. So, once you get your vehicle to start, drive it to a mechanic so they can repair the alternator.


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