How Long Will a Car Run Without Alternator?

Many car parts offer top-notch service without any glitch for many years, but you may not have that much luck when it comes to the alternator. In some car models, alternators go bad rather quickly than expected. How long will a car run without alternator? Knowing this will help you stay prepared for the most adverse situations.

Car Alternator: What Is It and How Does It Work?

The alternator is a car part that supplies continuous charges to the car battery. Because of the power it provides, the electrical systems and computers of a car can function. Its purpose is to keep the electrical system performing. 

When the battery starts the motor engine, the alternator makes it run. If it becomes faulty, the car battery drains faster than usual. So, if your battery is having some problems, it is wise to check the alternator too.

car alternator
An alternator supplies power to the battery. (Source: Mitch Barrie / Flickr)

Typically, an alternator lasts about 100,000 to 150,000 miles or about seven years. However, some mechanics claim that it has a shorter lifespan, about 80,000 miles.

Multiple factors have an impact on the lifetime of an alternator. Some of these are, quality of the car parts, the number of electronics equipment getting power from the alternator, and car driving conditions.

How Long Will a Car Run without Alternator

Once the alternator stops working, the car battery is cut off from the power supply. It will run on its own for a while until it runs out of charge. How long will a car run without alternator?

It entirely depends on the capacity of the car battery. If the battery does not have a full charge, the vehicle may run from 5 to 30 minutes. The runtime will increase in case of a fully charged battery.

Another factor that affects the runtime is the car model. Let’s see how long various car models will survive when the alternator gives up:

Old Model Gasoline Car: Driving a gasoline-run car in daylight will consume little energy from the battery. Since there are no headlights, only the spark plug and the car’s computer will drain the battery. If the vehicle model is from the 1960s or so, you can drive up to 50 miles with a fully charged battery.

Old Model Diesel Car: If you are running a diesel car that does not come with spark plugs, you can run it further compared to a gasoline car. If the car model is a real old one, there are chances that you can run it till the fuel lasts.

Latest Model Car: If the alternator fails in a car manufactured in the 90s or later, the battery will not last long. Brand new car models these days have computers, sensors, and various electronic displays, which will extract energy from the battery. As a result, the battery will last a shorter time.

Cars like Mini Cooper have electric power steering that rapidly drains the battery. Models with computer-controlled automatic transmissions will also consume more battery and let you drive fewer miles without an alternator.

Start Car Engine: When you have to start your car without an alternator, a significant amount of battery energy is drained. So, if you need to run your vehicle without the alternator, never turn it off once you have started.

How to Know If Your Alternator Is About to Die

As you now know how long will a car run without alternator, it is better to learn the warning signs of an alternator whose life will end soon. Detecting these symptoms early will save you from being stranded on a road with a dead car.

  • Pulsing headlights. At night, the headlights will suddenly become dim from bright if the alternator is about to die.
  • Some faltering alternators stop working when you use them to charge multiple electronics simultaneously.
  • If an electrical burning smell comes from your car alternator or the battery, the alternator might have reached its end.
  • The turning on of alternator warning light or other dashboard warning lights also indicates a struggling alternator.
  • If there is a dying alternator in your car, the radio or other electrical components will stop working at times. It can also cause a squealing noise in the engine.
bad alternator symptoms
An alternator can stop functioning for various reasons. (Photo: dave_7 / Flickr)

All good brands offer a decent warranty on car alternators, from one to three years. You can prevent your alternator from premature wearing by following these tips.

  • Do not start your car in the wrong way.
  • Do not overload your vehicle by installing extra electrical accessories.
  • Check if there is a tight belt or leaking fluid. Both these can harm the alternative bearing


FAQs on Car Running Without Alternator

  1. What happens if you drive a car without an alternator for an extended period?

Driving without an alternator for an extended period can lead to a discharged battery, causing the car to stall. It can also damage the battery and other electrical components if the vehicle relies solely on battery power.

  1. Can you jump-start a car with a dead alternator?

You can jump-start a car with a dead alternator, but it’s a temporary solution. The car will run using the power from the jumper cables and the donor vehicle’s alternator. Once you turn off the engine, the car with the dead alternator is likely to stall.

  1. Can you charge the battery separately if the alternator fails?

Yes, you can charge the battery separately using an external battery charger. This can provide enough power to start the vehicle and drive it to a repair shop if the alternator fails. However, this is a temporary solution and doesn’t address the underlying alternator issue.

  1. Can extreme weather conditions, such as extreme heat or cold, affect alternator performance?

Extreme weather conditions can affect alternator performance. Extreme heat can lead to overheating and damage, while extreme cold can increase strain on the alternator and electrical system. 

Proper maintenance and protecting the alternator from extreme conditions are advisable.

  1. Can you replace the alternator yourself, or is it a job for a mechanic?

Replacing the alternator is a complex task that typically requires mechanical knowledge and tools. While some experienced individuals may attempt it, it’s generally recommended to have a qualified mechanic perform alternator replacement to ensure it’s done correctly.


An alternator is a vital car component. Without it, your battery will not get the power it needs. 

A dead alternator will also disrupt the overall function of your motor car. When you have a fair idea about how long will a car run without alternator, you can go to the nearest service station and get its replacement.