Driver's Guide

Can You Drive a Car with a Bad Alternator?

With a bad alternator, you may find yourself gambling about driving your car. Moreover, the alternator powers most of the car’s electronic components. But can you drive a car with a bad alternator? Generally, if fully charged and perfectly functioning, the battery should run up to 25 miles or roughly 30 minutes on a bad alternator. If you run out of power, you will need to tow with a chain or a tow company.

That said, this publication covers everything you need to know about driving a car with a bad alternator, the risks or safety measures, as well as the cost of replacing it.

Can you drive a car with a bad alternator?

Can you drive a car with a bad alternator

You can drive a car with a bad alternator, but only for a limited time. Depending on how bad your alternator is at the time, you could be able to drive for as long as 30 minutes before it stops and may not restart unless jumped.

If the alternator problem is new, your battery probably still has juice in it, so you may be able to drive a car with a bad alternator. So, you simply turn off all non-essential systems in your car while driving. Also, most experts think you can probably drive your car for up to two hours before it dies.

One crucial thing to remember is that if you need to start your car while it doesn’t have a working alternator, you do not turn off the engine after it starts. Starting your car consumes a significant amount of energy from your car battery, so there is always the possibility that you will not be able to start your car again under these conditions.

How to run a car with a bad alternator

An alternator is a device that charges a car’s battery. When it fails, the battery quickly drains. So, you generally do not want to drive a car with a bad alternator.

Suppose the alternator is failing or has failed. You can probably drive the car for a short distance or for a short length of time, allowing you to get to a service station or automotive parts store for a replacement alternator. Keep the following in mind while running a car with a bad alternator:

a. Disable auxiliary things

Turn off any auxiliary things that could be on, like the radio, lights, windshield wipers, air conditioner, or heater.

b. Drive a short distance only

Drive the car for short distances only and avoid using electrical systems such as air conditioning, radio, or power windows.

c. Drive carefully in busy locations

Traffic jams may deplete the battery. Choose a parking area to park in until traffic is less heavy.

d. Don’t stop the engine

Keep the engine running when you stop, so that you can recharge the battery.

e. Contact a mechanic

Finally, head straight to the local service station or car parts store and get a new alternator. Install the new alternator yourself or have it done. Before you go, make sure your battery is fully charged.

Is it safe to drive if alternator is bad?

Generally, it is not safe to drive a car with a bad alternator. The alternator is responsible for supplying power to the car’s electrical system and recharging the battery.

When your car has a bad alternator, it begins to rely only on the battery to power its numerous functions, which is why your car’s battery depletes so quickly without a functional alternator.

If your alternator is bad, other problems could put you in danger on the road.

  • First and foremost, the engine in your car will become exceedingly unreliable. This can entail not just being difficult to start, but also stalling out in rush-hour traffic.
  • Additionally, if you drive a car with a bad alternator after dark, you may discover that your car’s headlights become significantly dimmer, making it more difficult for you to see and for others to see your car.
  • A bad alternator can also cause your dashboard and other car electronics to fail, which is not a pleasant experience while driving.
  • Last but not least, expect to smell rubber burning or other chemical-like smells emanating from your car. If this occurs, it typically signifies that wires are burning or that the alternator belts are overheating, both of which are likely reasons for your car’s electronics going berserk.

Does alternator affect car battery?

An alternator can affect a car battery. However, it is not necessarily a direct effect. The alternator’s primary function is to generate electricity to power the vehicle’s electrical systems and recharge the battery while the engine is running. If the alternator is not functioning properly, it may not be able to recharge the battery fully, which can lead to a dead battery. 

Nevertheless, it is customary to believe that if one fails, the other will suffer as well. While this is true to some extent, it is not as dramatic as it appears.

When it comes to newer cars, a bad alternator does not always mean that the battery is dead. Yet, some situations may cause the alternator to damage even a fresh battery.

When dealing with a bad alternator, here are some things to keep an eye out for.

1. Overcharging

A bad alternator can cause your battery to overcharge. This might cause early damage to battery cells, reducing the lifespan of your car battery. It is important to note that prolonged radiation exposure will harm even a brand-new battery.

2. Ripple voltage

Another issue that a bad alternator can cause is ripple voltage. This is when the alternating current passes through the rectifier of the alternator.

A stray ripple voltage can also damage the whole electrical system of your car, which can be fatal.

3. Inadequate charging

While a bad alternator can cause overcharging, it can also cause undercharging.

An inadequate power source for your battery can soon exhaust its power. The constant cycle of charging insufficiently and promptly draining your battery can also reduce its life.

4. Charging irregularities

Irregular charging happens when your car’s alternator charges the battery in spurts. This makes the power supply unpredictable.

This forces the engine to rely exclusively on the battery for power. Once the battery becomes the primary source of electrical power for the car, it quickly drains.

Cost of alternator replacement

When your car needs a new alternator, you won’t have to worry about a repair that will cost thousands of dollars.

In most cases, replacing your alternator is one of the most cost-effective repairs you can do to your car. You should expect to pay anything from $100 to $400 to get your alternator replaced—Your Mechanic.

Of course, this implies that no additional parts require replacement. If you tried to drive as much as possible with a bad alternator or no alternator, it is always conceivable that your car sustained more damage, especially if you observed rubber or chemical smells indicating that wires or belts were burning.

Thankfully, most alternator repairs simply require the serpentine belt to be replaced. If your car requires a serpentine belt replacement, the repair price will likely rise by $25 to $50.


How long can you drive with a bad alternator?

As long as your car’s battery is completely charged, you can normally drive for 25 to 30 minutes. Since the alternator is a key part of the battery’s power system, it needs to be fixed as soon as possible.

What happens if the alternator is bad?

If the alternator is bad, the battery will quickly lose its charge, and your vehicle will shut down faster. Additionally, the electrical system may fail, causing issues with lights, radio, and other electronic components.

Will driving with a bad alternator ruin your battery?

Your car can only run for a very short time with a bad alternator because the alternator charges the battery when the engine is running. Once the battery discharges, the vehicle will die and fail to restart.


If you drive a car with a bad alternator the battery won’t run for long but it should last long enough to get you to a mechanic. If you don’t fix the bad alternator, it can cause a number of problems such as electrical issues and potential failure to start the car and can also affect other parts of your car. That is why routine maintenance and check-ups are essential.

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Bernard Juchli

Bernard Juchli is an experienced racer, mechanic and team owner who trusts Avon Tyres.Bernard is the lead driver and force behind his Big Dog Garage Race Team. He is the General Manager and Chief Mechanic of Jay Leno’s Garage. Bernard and his crew of seven are responsible for all repairs, restoration and fabrication of Jay’s incredible automobile and motorcycle collection.

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