It is simple mechanics. Your car battery is what starts your vehicle. However, it is the alternator that keeps it running. For the unfortunate souls who realize that this vital part of the vehicle is failing, how long will a car run without an alternator and what can you do to elongate the vehicle’s ability to function? 

Without this essential component, your car will only function for up to two hours and as little as five minutes. Those with an older car model or a vehicle that runs on diesel will have the most run time. Moreover, if you keep the car running until you get to your final destination and make sure to turn off as many unnecessary electronics as possible, you can elongate your battery life. 

How Long Will A Car Run Without An Alternator?

The ability for a car to run without an alternator is highly dependent on a handful of factors. These include the type of vehicle that you are driving, the charge of the battery when the alternator dies, the amount of electrical equipment that you are using, and whether or not the car is running when the alternator fails. 

However, for most vehicles, expect as much as two hours of run time and as little as five minutes. Based on the speed at which you are traveling, this could be as little as a few miles or up to 100 miles away, if you are lucky!

1. Vehicle Information

The first determining factor of how long a car will run without an alternator is the age of the vehicle. Newer models are prone to have less life because they are equipped with advanced electrical systems that draw more energy from the battery.

Conversely, older model cars lack these bells and whistles, giving them more longevity when this vital component of your car malfunctions.

Another factor is if your vehicle is fueled by gasoline or diesel. Gasoline-driven cars require spark plugs to start the engine. These parts pull power out of the battery. Alternatively, diesel cars do not require this component. Therefore, these vehicles can run longer without an alternator. 

Interestingly enough, the only drivers who do not need to worry about this problem are those who have electric cars. That is because these vehicles do not have an alternator. Instead, they utilize electric motors with rechargeable batteries. This is why they have to charge their vehicles in between trips. 

2. Battery Charge

According to the experts at J.D. Power, “while the car is off and the battery is resting, the multimeter display should show a reading of 12.2 to 12.6 volts (full charge). This voltage range means the battery is in good condition for starting the vehicle. If the measured reading is less than 12.2 volts, the battery’s resting voltage is weak, which means it most likely needs to be charged or replaced.” 

For those who find themselves with a broken alternator and are needing to replace their battery sooner rather than later, it is likely you will only make it down the road a few minutes before your engine dies. In contrast, those with a full charge have the ability to make it up to two hours down the road, when not using other elements in the vehicle. 

3. Electrical Output

The lovely amenities that come with modern cars like your car’s computer, the stereo system, climate control functions, the windshield wipers, and the headlights all draw their power from your car’s battery. Thus, when the alternator dies and these components continue to be used, the battery will drain quickly.

This, in turn, will quickly diminish the time you have to continue driving down the road. Therefore, when you start to notice signs that the alternator is failing, turn off these extra functions. This will lengthen your battery life and allow your car to run a bit longer. 

4. Engine — On Or Off

The J.D. Power experts further note that “the moment that the vehicle is turned on [is the moment that] the battery is under the most draw because of the higher amount of energy needed to drive the starter motor. If it falls below 10 volts, it means the battery does not have sufficient turnover strength and is prone to failure.” 

With a working alternator, this energy is quickly replenished. However, when the alternator is out of commission, it takes an exorbitant amount of power to restart the engine again. Thus, it is best to conserve as much voltage as possible. This will help to ensure that you won’t require a tow later.

Therefore, if your alternator dies while the car is still running, do not turn the vehicle off until you reach your intended final destination. 

What Is An Alternator?

An alternator is a generator that converts mechanical energy into electrical energy in your vehicle. In layman’s terms, this is the device that continuously recharges your car’s battery. Without it, the battery’s power will quickly drain, leaving you in a bit of a lurch.

This crucial component of your car should last anywhere between 80,000 to 150,000. However, this is dependent on if you conduct routine maintenance on the vehicle.

Regular oil changes and ensuring that your fluid levels are consistently topped off are both fantastic ways to prevent issues from arising. Unfortunately, even with the most meticulous care, if debris, engine fluids, or other contaminants enter the alternator, this can cause it to fail sooner. 

How To Tell If Your Alternator Is Failing?

The alternator is the apparatus that keeps the main components of the car functioning. This means that it is actually quite easy to tell when it is starting to fade. First, you will notice that it takes longer for the car to start. This can also be accompanied by sputtering or squealing sounds. 

While the car is running, another sign of alternator issues is failing electronics. This can include your blinker not working or the windows being slow to open. Moreover, you may notice the radio randomly turning off or your dashboard lights suddenly looking very dim. Other red flags of a bad alternator are a burning smell as well as your car stalling out. 

Finally, the most obvious sign that something is going awry under the hood is when your check engine light pops on. This is not an indicator that should never be ignored. Remember that, as mentioned above, before the alternator completely sputters out, other problems will occur. Acting promptly is imperative. 

What To Do When Your Alternator Starts Failing?

When these things start happening, it is imperative that you get to a mechanic as soon as possible. Your car may run without an alternator for another two hours.

However, what is important to remember is that without your alternator, other essential car functions will rapidly begin to fail as well. Waiting too long to address this problem will endanger your life. It could also get you stranded on the side of the road.

Moreover, traveling at high speeds without properly functioning equipment can be a recipe for disaster. Therefore, get off of any major roads and avoid traveling on overpasses or bridges. Additionally, steer clear of stop-and-go traffic. This is a quick way to drain your car’s battery. 

Furthermore, until you can reach a car maintenance specialist, drive in the far right lane. This guarantees that if your car suddenly stalls or shuts down completely, that you, your passengers, and the vehicle remain safe. 

Finally, it is important to remember that if you can make it to a mechanic before the engine completely dies, to make sure that they recharge the battery after replacing the alternator. 

Frequently Asked Questions

If I am without an alternator, is there any way to restart my car once the battery has died?

Your first option is to have someone jumpstart your car so that you can make it to your intended destination. However, if you are unable to find this kind of help, you can always purchase another battery to get you further down the road.

This can buy you about an hour if you avoid using your electronics and keep the vehicle running. While this may seem like an expensive solution, sometimes it can be a cheaper alternative to towing the car.

Final Thoughts

A failing alternator is a very expensive problem to have, but this machine is also the heart and soul of your vehicle. Thus, if you notice signs of failure, take initiative to get your car to a mechanic before the problem worsens.

Remember that once these problems begin, your car will only run for up to two hours without an alternator. However, this scenario will only occur if you are strategic with what you use during the drive.

Lastly, the best way to avoid this issue is to take your car in for regular maintenance. Many times, minor problems can arise that will cause the alternator to fail before those seven years or 150,000 are up.

These can include wiring problems, a bad fuse, or the need for updates to your car’s computer. Discovering and addressing these issues early can prevent a bigger headache from happening while you are on the road. 

If you’re also experiencing problems with your car’s Bluetooth connection, we have a guide on “Why Does My Bluetooth Keep Disconnecting In My Car?” that might help. And if you’re wondering if it’s safe to put gas in a running car or why your car’s doors keep locking and unlocking on their own, we have blog posts on those topics too. Don’t let these issues go unresolved as they could potentially cause more problems for your car in the long run.


Welcome to my car seat blog! As a mom of 3, I put together with other hard-working moms a highly informative one-stop car seat resource, full with many reviews and buyer guides. I hope you find it invaluable. Thank you for trusting me & my team! - Keren

Keren Simanova

Welcome to my car seat blog! As a mom of 3, I put together with other hard-working moms a highly informative one-stop car seat resource, full with many reviews and buyer guides. I hope you find it invaluable. Thank you for trusting me & my team! - Keren