How Long Can You Drive With a Bad Alternator?

Did your car develop an alternator problem while driving, and you are wondering how long can you drive with a bad alternator?

Look no further because you are in the right place.

In this article, we explain the causes of alternator failure, how long can you drive with a bad alternator, what to do when you have a bad alternator and what to do to prevent the alternator from failing.

We will also answer any questions you might have about driving with a bad alternator, alternator repair and replacement, and lots more

Let’s begin

How Long Can You Drive With a Bad Alternator?

You can drive with a bad alternator for as long as your vehicle has power stored in its battery. If your battery is fully charged, you can only drive your vehicle for approximately twenty-five miles with a bad alternator before the battery is depleted. Twenty-five miles translates to a maximum of thirty minutes of driving.

When your alternator gets bad, your car won’t be able or will find it difficult to start because the battery life will be significantly down.

Though let us assume you are driving and the alternator stops working; in this case, the car will go as far as the battery can carry it. It is often a very short distance, and after that, the battery will be entirely down, thereby shutting down the car.

If you are driving and notice that your alternator is bad, the best thing to do is drive to a nearby mechanic immediately.

However, do not keep driving with it as though everything is fine because you will get stranded on the road if you do not get to the mechanic immediately.

Signs of a Bad Alternator

How Long Can You Drive With a Bad Alternator

1. The Alternator Warning Light Turns On

The first sign that displays when your charging system gets bad is the dashboard warning light.

There is a special light for the alternator; it starts displaying or illuminating when there’s a problem with the alternator. Some older cars use the check engine light, while some will display GEN which means Generator.

There’s a sensor responsible for triggering the warning light base on the alternator voltage output. This sensor is part of the car computer system.

When your car voltage is high or low to a certain limit, it will affect your electronics and electrical components, turning on the warning light.

When your alternator produces a voltage out of 13V and 14.5V, it is said to be healthy, and if it has a voltage too high or too low, it is faulty.

Therefore, your car radio, headlight, and the windshield will require more work from the alternator to maintain the correct voltage.

The alternator voltage can be high or low when it is on Fritz; this will also trigger the warning light, although when the alternator is beginning to show signs of a problem, you may experience a flicker from the warning light.

2. Dim or Overly Bright Lights

Electrical failure is one of the signs of a faulty alternator because the alternator is the sole source of power for your car’s electrical components.

When the failure starts, you will start observing dimming of interior lights, odd brightness, headlight flickering, your car radio might even stop working, and its dashboard warning light will turn on.

These signs are apparent electrical faults, mainly linked to the alternator. However, there is the possibility that your car’s electrical component is acting up because of the way it is programmed.

There are sets of priorities programmed in modern cars that determines where the alternator should send electricity.

The major factor to this priority is safety; you will first notice that your car radio has gone off before any other component like the headlight when your car starts having alternator problems.

3. Strange Noises

Noise or sound is part of a car’s way of functioning. However, some noises indicate something is wrong and should be attended to as soon as possible.

Whining or growling sound is very common in the faulty alternator.

Depending on the type of car, the drive belt or serpentine belt will work together with the crankshaft pulley to run the alternator.

However, the crankshaft pulley does not spin like the alternator pulley; that will spin faster, around two to three times to generate the required amount of power at a lesser speed.

The whining or growling noise happens when the drive belt does not properly align with the alternator’s pulley or is worn out. When such happens, it is a vital sign of an alternator problem.

Keeping a bad alternator on for a long time is not good for your car engine; it can create a bigger problem for your car. Leaving the bad alternator for too long will result in rattling noise inside the engine, resulting from a damaged engine bearing.

4. Unpleasant Smells

A bad alternator can generate an unpleasant smell because of overheating and melting electrical components.

Another reason for this is that the alternator wire can be melting, releasing a rubber-like smell at some point; if not attended to, the alternator will ultimately fail, and the car will shut down within a short time.

5. Bad Belts

Bad belts or faulty belts are common car problems; however, sometimes they are linked with a bad alternator.

A missing belt can cause the alternator to develop a fault because the motion will be affected. However, a faulty belt won’t be difficult to notice, so you will quickly see it and possibly fix it when you open the hood.

Look out for signs like large wear, cracks, and related damaging signs when you open the hood

to examine the belt. Also, ensure that the belt tension is not too loose or too tight; it should be the right amount of tension specified for your car; else, it may affect the alternator.

When you notice that you can not handle the belt repair or change, please call your mechanic to do the fixing than doing it yourself and create more damage.

6. Regular Stalling or Difficulty Starting

Stalling or hard starting is associated with a faulty alternator; however other issues can also create this problem.

A faulty fuel pump and a faulty battery can cause hard starting or stalling. Therefore be careful when examining the car to identify the problem correctly.

When you confirm that the alternator is the problem, a closer look at the problem will suggest that the alternator is no longer charging the battery, causing the battery to die.

Remember that your car needs the power to ignite the engine, and if your battery can not produce power, your vehicle won’t be able to start.

Your car spark plug won’t be able to gain the right amount of electricity from the alternator, thereby causing stalling or difficult starting. Sometimes the engine can get turned on and stalled because of this problem.

Also Read: How To Test An Alternator (3 Best Ways)

How Long Do Alternators Last?

How Long Can You Drive With a Bad Alternator

Ideally, your car alternator is designed to last as long as the lifespan of your car; however, this is only applicable in theory; in a practical sense, the alternator will develop issues in the long run.

It is pretty not certain how long an alternator will last because of the factors that affect how it should stay.

Most cars will attain around 40,000 miles to 100,000 miles before developing any alternator problem, especially if they are new cars. Some cars can even go beyond without an alternator problem.

Older cars do not have any electronic or electrical components for an alternator to power; they mostly have to power radio, exterior and interior lights, and other electrical parts.

Whereas in modern cars, the alternator will have to carry more components like the heater, the GPS, the air-conditioning, power window, electronic doors and windows, heated seats, and other complex electronic components.

All these will require power, which means the alternator will have to generate or produce more power, which entails the alternator doing more work or under more stress.

Also Read: How Long Does It Take to Replace an Alternator?

How Do I Know if It’s a Faulty Alternator or Battery?

Three processes happen when starting a car engine and running it. This process is

  1. The starter motor will receive a jolt of energy from the battery to power the car
  2. The engine power up the alternator and
  3. The alternator recharges the battery.

To verify if the battery of your car or the alternator is the fault with your car stalling or hard starting and to know which one to replace, jumpstarting your car will help clarify this.

For example, when you jumpstart your vehicle, and the engine comes up but dies down almost immediately, it indicates that you have an electrical fault, which could mean that the alternator may not be charging the battery.

If the car started and didn’t die down, it keeps running but won’t start for a second time; then the fault could be coming from the battery.

Another way to determine the actual fault is by using a voltmeter. For example, when checking electrical differences at two points on a circuit, a voltmeter measurement can give you the answer you are looking for. It is the fastest method to verify the actual problem.

Also Read: 10 Signs Of A Bad Alternator

Can I Drive With a Bad Alternator?

You can run your car with a bad alternator, but most times, this is only possible when the alternator starts failing; else, it is almost difficult or impossible to run the car in severe alternator cases.

When your alternator stops working, it will be impossible to start your car because the car battery will be dead.

Can My Alternator Fail While I’m Driving?

How Long Can You Drive With a Bad Alternator


Alternator failure can happen at any time, even when driving. The good news is that alternator failure while driving is not a dangerous situation, unlike brake loss.

When your alternate fails, your car battery will no longer be charging; instead, it will give out all the power it has, and when it is done, it will run down and gradually shut down your engine.

When your car’s alternator stops working while driving, you should switch off all the electrical appliances in your vehicle and park in a safe place.

New cars do come with power steering, and for this reason, they could present a challenge when the alternator stops working while you are driving.

Therefore, you are advised to stop driving the car when you notice an alternator problem for safety purposes because it can lead to a severe accident.

It can also cause overheating of your car engine, costing as high as $2,500 to $4,500 to fix. So not driving the car until the problem is fixed will save you a lot.

Remember that snapped serpentine belts can cause alternator failure, affecting other components of your car, such as the Water pump.

What Causes an Alternator to Go Bad?

Age is a factor that could cause an alternator to develop a problem, especially when the car has reached about 10,000 miles. However, other factors can cause alternator failure. Such factors are:

1. Fluid Leaks

If your car engine oil or your power steering fluid is leaking, this fluid can find its way to the alternator, causing malfunctioning or failure.

2. Bad Driving Habits

The way you handle your car determines how long it will last. Reckless driving will affect your alternator lifespan. Putting on all your car’s electrical components will increase the stress on the alternator, causing its possible damage.

Water is not friendly to an alternator. Therefore, if your car’s alternator is located under the engine where water can reach it every day, the alternator will malfunction in no time and may even get damaged.

How Much Does an Alternator Cost to Replace?

Alternator replacement costs can range from $500 to $1000. Several factors can affect alternator replacement costs, such as the car’s make, model, and repair location

However, rebuilding an alternator is possible and even pocket-friendly compared to buying a new one. The cost of rebuilding is around $70-$120, excluding the labor cost. The cost of labor ranges from about $80-$120. So you will discover you will spend way lesser than buying a new one.

What Should I Do When Experiencing Alternator Trouble?

How Long Can You Drive With a Bad Alternator

The best thing to do when you notice your car’s alternator is bad is to call your mechanic or a nearby good mechanic to come and look at it.

This is because driving with a bad alternator is a terrible idea, and it may create more problems, which will add to the cost of repair.

Also Read: Alternator Repair Options And Which You Should Choose

Can You Jump Start My Battery With a Bad Alternator?

It is possible to jumpstart your car with a bad alternator. This is because the jumpstarting of a vehicle is the addition of voltage to the battery, and when the jumper cable is removed, voltage is no longer added to the battery.

You have limited time running your car with a bad alternator after jumpstarting. Therefore, you must maximize this time by taking the vehicle to the nearest good mechanic for your alternator repair. If not, your car battery will run down again, shutting down the engine.

For more information on how to jumpstart a car with a bad alternator check out this guide: Can You Jumpstart a Car With a Bad Alternator?

Do I Need to Replace My Battery if I Replace My Alternator?

Your car battery is more likely to be completely dead when you have a damaged alternator. Therefore, when you replace the alternator with a new one, it is better to get a new battery or recharge the old one.

You will need to get an alternative way of charging the old one; this is where the trickle charger comes in. A special battery charger is competent in deep cycle battery charging and can fully complete the battery charge.

This kind of charge will be a low voltage for an extended period. The lead plate will maintain this voltage as the battery gradually gets its operational voltage.

This will also help the battery not experience shell shock when charging at a fast high voltage.

How Long Can You Drive With a Bad Alternator

Frequently Asked Questions – How Long Can You Drive With a Bad Alternator?

How Long Will a Battery Last With a Bad Alternator?

You can drive with a bad alternator for as long as your vehicle has power stored in its battery. If your battery is fully charged, you can only drive your vehicle for approximately twenty-five miles with a bad alternator before the battery is depleted. Twenty-five miles translates to a maximum of thirty minutes of driving.

What Happens if You Keep Driving With a Bad Alternator?

Driving with a bad alternator may not be as life-threatening as a failed brake, but it is unwise. A bad alternator can damage other components of your car if It is not repaired or replaced. It can also keep you stranded in an unsafe place. Therefore as soon as you notice the symptom of a bad alternator, drive straight to your mechanic.

How Much Does It Cost to Change the Alternator?

Alternator replacement costs can range from $500 to $1000. Several factors can affect alternator replacement costs, such as the car’s make, model, and repair location

Will a Bad Alternator Ruin a New Battery?

Yes, a bad alternator can drain down and even kill a new battery. Therefore, when you feel like changing your battery, maybe because it runs down quickly, please verify that the alternator is in good shape; otherwise, the new battery could get damaged if it is bad.

What Causes an Alternator to Fail?

Age is a factor that could cause an alternator to develop a problem, especially when the car has reached about 10,000 miles. However, other factors that can cause alternator failure are oil or similar car solvent leakage. In addition, water, engine oil, or power steering fluid are unfriendly to the alternator.

How Can I Prevent My Alternator From Failing in the Future?

Regular maintenance is a sure and valid way to prevent your car from having alternator problems. Paying attention to the symptoms is also very important. Observing the battery and your check engine light is as well vital.

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