Alternator failure causes?

5 Causes of an Alternator Going Bad

  • Dead Alternator.
  • Computer Problem.
  • Wiring Problems.
  • Bad Fuse.
  • Broken Pulley or Broken Belt.

What kills an alternator?

Running in full charge mode continuously can kill an alternator, so trying to have your new alternator try and charge your dead battery can result in immediate alternator failure.

Do alternators fail suddenly?

The alternator is a key component in running the electrical systems in your car. When your alternator begins to fail it can cause a variety of different electrical problems in your car, and eventually cause a breakdown. Alternators can go bad suddenly, or slowly over time.

What are the signs of a bad alternator?

4 Symptoms of a Faulty Alternator

  • Car Won’t Start. A dead battery almost always lies behind a car that won’t start.
  • Engine Stalling. A dead alternator almost always leads to a car that won’t start.
  • Electrical Issues. A dying alternator can lead to a wide range of other electrical issues.
  • Unusual Sounds.

What is the average life of an alternator?

“Its primary job is to keep the electrical system up and running in place of the battery. The battery’s job is to start the car, and the alternator keeps it running.” Gunning says an alternator typically lasts about seven years — or about 100,000 to 150,000 miles, says Waits.

How much does it cost to fix the alternator?

When your car starts having electrical problems, it’s a sign you need an alternator replacement. Considering the price of a new alternator as well as labor, you should expect to spend anywhere between $500 and $1,000 to get a new one for your vehicle.

Can I drive with a bad alternator?

Technically yes. If you have a bad alternator or you’re just starting to experience car alternator problems, you can still drive it; however, it’s best not to. If your alternator has stopped working entirely, you have minimal time before your car stalls and won’t restart since you have a dead battery.

How do I know if I need a new alternator?

7 Signs of a Failing Alternator

  1. Dim or Overly Bright Lights.
  2. Dead Battery.
  3. Slow or Malfunctioning Accessories.
  4. Trouble Starting or Frequent Stalling.
  5. Growling or Whining Noises.
  6. Smell of Burning Rubber or Wires.
  7. Battery Warning Light on Dash.

How do you tell if its your alternator or your battery?

If your engine won’t turn over or takes far longer than usual, it’s time to grab the jumper cables and attempt a jump-start. If your engine starts and stays running but won’t start again later, it’s likely a battery problem. If your vehicle immediately stalls, it’s probably a bad alternator.

How do I know if it’s the battery or the alternator?

An illuminated dashboard light can indicate a problem with an automobile charging system. However, a very simple way to check if the alternator is working is to run the car and disconnect the positive terminal of the battery. If the vehicle stops running, then you probably have a bad alternator.

What happens when the alternator fails?

When an alternator fails, these systems no longer receive the correct amount of electrical energy. This can cause these systems to operate erratically or not at all, resulting in stalling and poor running of the engine.

How long does it take for a bad alternator to drain a battery?

In this situation, the battery could last as little as 30 minutes. If you are lucky and could get up to two hours. Note: In case you have to start the car without an alternator, don’t turn off the engine once you’re going. Starting the car flattens the battery down quickly.

Alternator Failure Causes

Automobile Repair Library, Auto Parts, Accessories, Tools, Manuals and Books, Car BLOG, Links, and more. Index byLarry Carley (c)2019 All rights reserved. The alternator is responsible for keeping the battery charged as well as supplying electricity to the vehicle’s lights and other electrical components. The failure of the alternator will cause the battery to discharge and, in certain cases, will prohibit the car from starting. There may be a charging problem if the charging voltage measured with the engine running is not 13.5 volts or greater.

Although it is possible that the problem is caused by a failure in the wire that links the alternator to the vehicle’s electrical system, it is also possible that the problem is caused by a malfunction in the Powertrain Control Module (PCM), which governs the charging circuit.

Many auto parts stores provide a bench tester that may be used to monitor the voltage and current of an alternator’s output.

If the alternator passes the bench test, the problem is not with the alternator, but with a wiring defect or a problem with the PCM.



One of the most common reasons of a poor or non-existent charging output from the alternator is the failure of one or more diodes in the alternator’s rear end. The ‘rectifier’ assembly has three diode pairs (for a total of six diode pairs) that convert the alternator’s alternating current (AC) output to direct current (DC) (DC). This is required due to the fact that the fuel pump, fuel injectors, ignition system, engine computer, lighting, and other onboard electronics and electrical accessories all rely on direct current (DC) to function properly.

A bad diode may fail to pass any current at all, resulting in a reduction in the amount of current output from the alternator; alternatively, a bad diode may leak alternating current into the vehicle’s electrical system, resulting in a ripple voltage that can interfere with the normal operation of certain onboard modules.

If this occurs, the battery will progressively deplete over time if the car is not driven regularly.

Perhaps there isn’t enough airflow through the alternator to keep the diodes from overheating, which is a possibility.

This is more likely to occur when the outside air temperature is high and the engine is left idling for an extended length of time with the A/C running, the headlights on, the radio, and so on.


Over time, the shaft bearings that allow the rotor to rotate inside the alternator might become worn down and need to be replaced. Bearings in a worn shaft can be noisy (making rumbling, buzzing, or squealing sounds), and they can eventually bind up and seize completely. When the alternator locks up, the drive belt is frequently snapped or thrown out of the way. In addition to dirt and water pollution, bearing failure can occur as well. A vehicle driven through water that is deep enough to splash or flood the alternator might harm the alternator shaft bearings, and perhaps the brushes and electrical components contained within the unit as well, causing it to fail.

Alternator bearings that have worn out can be changed by dismantling the alternator and replacing them with new ones.


An alternator is comprised of two sets of windings on the inside. Within the alternator is a rotor that rotates, which is encased in a network of wires called a winding. These windings generate a magnetic field, which induces current in the other set of windings, which are positioned around the rotor within the housing and generate a magnetic field as well (the field coils or stator). If any of the individual wires in the rotor or stator short out or break, it can cause the alternator’s output current to be reduced or perhaps shut down completely.

  • If any of the connections are faulty (for example, if they are loose, rusted, or damaged), the alternator’s current output may be disrupted.
  • Finding such issues may be impossible without doing a Voltage Drop Testacross all of the connections.
  • Electrical current can travel from the stator to the rotor, allowing the alternator to generate current.
  • By dismantling the alternator, old brushes may be replaced with new ones, and worn slip rings can be changed or polished to restore proper contact.

The exciter portion of the rotor generates voltage, which is then transferred to the revolving coils in the second section, where it induces current in the outer windings of the motor.


In order to properly repair an alternator, you must have a certain level of ability and competence, and certain alternators may not be rebuildable due to damage to the shaft, rotor, or housing. This, combined with the difficulty of obtaining internal alternator repair parts, means that it is usually faster and easier for the average motorist to simply replace a bad alternator with a new one, or with one that has been professionally rebuilt or remanufactured, rather than attempting to repair it.

They may be able to rebuild your old alternator for less money than it would cost you to purchase a new or remanufactured alternator from a parts store or from an internet retailer like Amazon.

We would not advocate purchasing an untested secondhand alternator from a salvage yard or online unless the vendor is prepared to accept the alternator back if it does not function properly.

Related Articles:

Checks for Payment How to Replace an Alternator (with Pictures) Problems with the battery’s disconnect The following should be read BEFORE disconnecting or replacing your battery. Identifying a Battery that is running low Testing of Batteries Starting Troubleshooting of the Charging System Starting Service for the Charging System Alternators with a High Output (Why You May Need One) Identifying and troubleshooting electrical problems Electrical Loads for Automobile Systems, Lighting, and Accessory Equipment Circuits Electrical in the Automobile To access AA1Car Automotive Technical Articles, please click here.

Make sure to check out our other websites as well: Carley Automotive Software is a company that develops software for the automotive industry.

What Do Alternators Do, and Why Do They Fail?

Invoicing and Acceptance of Charges A Guide to Changing an Alternator Having Problems With Your Battery The following should be read BEFORE disconnecting or replacing your battery: A Battery That Isn’t Working Correctly Tests on Batteries Starting Troubleshooting the Charging System Starting Customer Support for the Charging System Variable Frequency Drives (VFDs) with a High Output (Why You May Need One) Problem-solving techniques for electrical issues Electrical Loads for Automotive Systems, Lighting, and Associated Accessories Electrification in the Automobile You may read more about automotive technology by visiting

Remember to check out our other websites, such as the ones listed below: Carley Automotive Software is a company that develops software for the automotive industry.

Random-MisfireScan Tool Assistance from OBD2HELPRandom-MisfireScan Tool TROUBLE-CODES

6 Signs Of A Bad Alternator + Solutions & FAQs

Knowing the indicators of a damaged alternator early on may save you a great deal of time and money in the long run. But, what are the indicators of a failed alternator, and how can you tell?

In addition, what should you do if you are suffering alternator problems? The answers to those queries, along with a few other commonly asked topics, will be covered in this article, which will provide you with a better knowledge of your car’s alternator.

This Article Contains:

(Click on a link to be sent to a certain portion of the website.)

  • The Alternator: What Is It, and How Long Do Alternators Last? What is the best way to tell whether my alternator or battery is faulty? Is it possible to drive my car with a bad alternator? Is it possible for my alternator to fail while I’m driving? How Does An Alternator Become Malfunctioning? When it comes to replacing an alternator, how much does it cost? So, what should you do if you are experiencing alternator problems?

Let’s get this party started.

6 Signs Of A Bad Alternator

Let’s get this party going!

1. The Alternator Warning Light Turns On

The most typical symptom of a problem with your charging system is the presence of a dash light. Most automobiles manufactured within the previous decade should be equipped with a dedicated alternator warning dash light to alert the driver of an alternator problem. Some automobiles utilize their battery light or check engine light, but others may display the letters ‘ALT’ or ‘GEN,’ which denotes the presence of an alternator or a generator respectively. This battery warning light communicates with the computer systems in your car, which allows them to monitor the voltage output from the alternator.

Alternators with healthy voltage outputs should produce between 13V and 14.5V at the output.

If your alternator is having problems, the voltage will be either over or below the preset threshold, causing the warning light to turn on or off.

2. Dim Or Overly Bright Lights

The alternator is responsible for powering your vehicle’s electrical system, therefore electrical breakdowns are often one of the first indicators of a failed alternator. Perhaps you’ve noticed that your headlights are flashing or that the interior lights are fading or becoming unnaturally bright. It’s possible that your speedometer, tachometer, dashboard lights, or radio will cease operating at any time. These are telltale symptoms that there is a problem with the electrical system in your car.

See also:  Ford transmission slips? (Suits you)

For example, many new automobiles come with a pre-programmed set of priorities for where the alternator transmits power, which may save time and money.

3. Strange Noises

A large number of noises are produced by automobiles, some of which are entirely normal and others which might signify major difficulties. Agrowling or whining noise is one of the sounds associated with a faulty alternator. The alternator is driven by a drive belt or serpentine belt that travels in combination with the crankshaft pulley. When operating at lower speeds, the alternator pulley typically spins around two or three times faster than the crankshaft pulley in order to provide the power required.

Take cautious not to leave a defective alternator running for an extended period of time, since this might cause harm to your engine. If this occurs, you will most likely begin to hear rattling from within your engine, which is caused by worn engine bearings failing. One

4. Unpleasant Smells

If you notice a weird smell coming from your car, it might be because your alternator is working too hard or overheating, which is producing difficulties with the electrical system. Why? Because the alternator’s belt is always under stress — and because it is so close to the engine — it may begin to wear down over time, emitting a terrible odor of burnt rubber and becoming brittle. This might be the wiring of the alternator, and you could be on the verge of experiencing alternator failure if you notice something that smells suspiciously like an electrical fire.

5. Bad Belts

Bad belts, on the other hand, are a little less prevalent than electrical problems; yet, they can also be indicative of an alternator problem. It is common for a defective alternator to be caused by a loose or missing belt. Because a damaged belt is visible from the outside, it’s worth having a peek beneath the hood, even if you don’t intend to repair it yourself. It is possible to undertake a brief inspection of the belt to look for cracks, excessive wear, and other symptoms of wear and tear.

As a consequence, it may be better to avoid inflicting any extra harm to your car’s electrical system and to leave it in the hands of a professional repair instead.

6. Regular Stalling Or Difficulty Starting

Aside from an alternator problem, there are a variety of additional issues that might cause your automobile to stall often and have difficulty starting. Things such as a defective battery or a malfunctioning fuel pump might cause symptoms that are similar to one another, so make sure to examine everything else that is going on with your car to determine the source of the issue. If the alternator is the source of the problem, one possible explanation is that it is not charging your battery properly, resulting in a dead battery in your vehicle.

If your car continues to stall even after you have turned it on, it is possible that the spark plug system is not receiving enough current from the alternator to keep the engine going.

8 Alternator FAQs

The following are eight frequently asked questions and their respective answers about alternators:

1. What Is An Alternator?

The charging system of a car is comprised of three components: the car battery, the voltage regulator, and the alternator (or generator). Alternators, which are around the size of a coconut, are often situated towards the front of the engine. They receive power from the crank shaft, which turns the up-and-down action of the pistons into circular movement by rotating the shaft. The alternator in your vehicle provides electricity to electrical components in your vehicle, such as the headlights and windscreen wipers.

Alternators generate alternating current through the use of a stator and a rotor.

The power is then transferred to the automobile battery, which supplies the voltage required to operate the electrical system of your vehicle. While this is going on, the voltage regulator is making sure that the voltage remains consistent.

2. How Long Do Alternators Last?

The alternator should, in theory, last as long as your car, but unfortunately this is not always the case. It’s difficult to predict how long an alternator will survive because there are so many variables that influence its lifespan. Some automobiles may have alternator problems after 40,000 miles, whilst others may travel 100,000 miles without experiencing any problems. Recall that in previous automobiles, the alternator only had to provide power to a few items, such as the interior and exterior lighting, the radio, and perhaps one or two other electrical components.

All of these items require the use of your alternator’s electricity, increasing the stress placed on it.

3. How Do I Know If It’s A Faulty Alternator Or Battery?

In its most basic form, starting and operating an engine consists of three steps: first, the battery supplies a burst of energy to the starter motor, which in turn powers up the automobile; second, the engine is turned on; and third, the engine is turned off. As a result, the engine provides power to the alternator, which in turn recharges the vehicle’s battery. In order to determine if you have a faulty battery or whether your auto alternator has to be replaced, you should jump-start your vehicle.

The likelihood of having a faulty battery increases if your car starts and keeps running, but you can’t get it to start again using its own power.

When two points on a circuit are connected together, the electrical difference between them is measured by a voltmeter.

4. Can I Run My Car With A Bad Alternator?

In its most basic form, starting and operating an engine consists of three steps: first, the battery supplies a burst of energy to the starter motor, which in turn powers up the automobile; second, the engine is turned on and runs; and third, the engine is turned off and off again. The alternator, which is responsible for recharging the vehicle’s battery, is powered by the engine. You should jump-start your automobile if you aren’t sure if you have a faulty battery or whether your car alternator requires replacement.

Having a faulty battery is more likely than not the cause of your automobile starting and staying running but not starting again on its own power.

Consider obtaining a voltmeter as an alternative. The electrical difference between two locations on a circuit is measured using a voltmeter. It is often the most convenient to diagnose an alternator problem with an instrument such as a voltmeter.

5. Can My Alternator Fail While I’m Driving?

Yes, alternator failure can occur at any moment, even while you are driving your vehicle. Because of this, if your automobile alternator fails while you’re driving, it isn’t nearly as dangerous as losing control of the vehicle. If your car’s alternator breaks entirely while you’re driving, your battery will be able to provide all of the electrical power the car need to keep running. But only for a limited period of time. The battery has the capability of giving the necessary power. The size and condition of the battery, as well as the number of electrical accessories you are using, determine how long it will survive.

In the event that you are driving and believe that your alternator has ceased generating power, switch off all of the electrical accessories you can and pull over to a safe parking spot.

In such instances, refrain from using the vehicle at all.

A rebuilt engine may cost anywhere between $2,500 and $4,500, so it’s wise to avoid taking a chance on such a costly endeavor.

6. What Causes An Alternator To Go Bad?

The majority of the time, alternators fail as a consequence of wear and tear or excessive use. Some additional conditions, on the other hand, can cause an alternator to fail prematurely. The failure of the automobile alternator is frequently caused by fluid leaking from the alternator. A common occurrence is for engine oil or power steering fluid to make its way into the alternator, causing it to malfunction or fail completely. Your driving habits will also have an impact on the longevity of your alternator.

Final point to mention is that if the alternator is positioned near the bottom of the engine, there is a possibility that it may be subjected to water and salt infiltration.

7. How Much Does An Alternator Cost To Replace?

It is possible that an alternator replacement will be a costly endeavor. According on the year, make, and model of your car, the cost will vary significantly. When purchasing an original item from a dealer, prices can range from $420 and $850, and in certain cases, they can even be higher than that. However, it is frequently possible to rebuild the alternator for less money than it would cost to purchase a completely new part.

For removal and installation, as well as the rebuilder’s fee, a new alternator will often cost between $70 and $120. The rebuilder’s fee will typically be between $80 and $120. It is possible that you will pay additional labor expenditures.

8. What Should I Do When Experiencing Alternator Trouble?

As soon as you notice any problems with your car’s alternator, you should schedule an appointment with a technician to come out and check at it. We urge that you have a professional repair come to your driveway since driving with a malfunctioning alternator might result in other, more expensive problems down the road. However, make certain that your mechanic does the following:

  • ASE-certified
  • Provides a service warranty
  • Only uses high-quality replacement parts
  • And is a member of the Better Business Bureau.

It’s true that hiring a qualified technician might be more difficult stated than done. Fortunately, there’s RepairSmith—a mobile vehicle repair service that’s both accessible and convenient to use. WithRepairSmith:

  • You can schedule your auto repairs online in a quick and simple manner. Repairs and maintenance will be carried out by ASE-certified experts right from your driveway
  • Repairs and services are performed using only the most up-to-date technology and high-quality parts. The pricing will be disclosed up front and will be competitive. On all repairs, you are covered by a 12-month/12,000-mile limited warranty.

For an exact estimate of the cost of an alternator replacement and repairs, please complete this online form.

Final Thoughts

However, while your car’s alternator should be able to endure the whole life of the vehicle, there are situations when it fails prematurely. If you detect any issues with your vehicle’s electrical system, don’t overlook them since they might be an indication of a potential alternator problem. What you need to do is get in touch with RepairSmith. Following that, ASE-certified specialists will arrive at your home, ready to install a new alternator in as little as 30 minutes!

Starters and Alternators: Common Misdiagnosis

Diodes that have failed are a typical cause of alternator failure. The diodes are a component of the rectifier assembly, which transforms the alternator’s alternating current output to direct current. The charging output of the alternator passes through six diodes in the rectifier assembly before it is sent to the battery and electrical system for use. As a result, the larger the charging load, the hotter the batteries become. Normal driving and charging loads will not cause the diodes to fail, but rarely driving and short trip nighttime driving with lights and other accessories on can greatly increase charging loads and limit their life.

  • The alternator may still be able to provide enough current to fulfill the vehicle’s electrical requirements if only one or two diodes have failed; however, the current may not be sufficient to keep up with increasing loads or to keep the battery completely charged.
  • Failures of diodes can also result in alternating current (AC) leaking into the electrical system.
  • It is also possible for current to drain from the battery through the alternator when the car is not being driven because of a faulty diode.
  • The charging output of certain older vehicles is controlled by external voltage regulators, however many late-model vehicles are controlled by the PCM.
  • Excessive heat can also cause internal voltage regulators to malfunction.
  • A bench test will verify the diodes and internal regulator of the alternator and will tell you whether or not it is capable of delivering the rated current and voltage for the alternator.
  • If the starters and alternators perform adequately, but the car does not operate, the fault must be somewhere else in the vehicle.
  • Misdiagnosis is the most common reason for unnecessarily returned alternators.
  • Not only should you test your customer’s old alternator to see if it is defective, but you should also test a new or remanufactured alternator before it is shipped to ensure that it is in excellent working order.

Another consequence of misdiagnosis is that a perfectly excellent starter may be replaced when it is not essential. In order to determine whether a starter is turning quickly enough for dependable starting while not drawing excessive current, you must do a bench test.

7 Signs of a Failing Alternator

The alternator is a critical component in the operation of your vehicle’s electrical systems. The alternator is responsible for converting the energy from the crankshaft into electricity, which is then stored in the battery of your automobile. In operation, the alternator assists in the powering of your vehicle’s many electrical systems as well as the maintenance of your battery’s charge. Your alternator’s failure can result in a range of various electrical difficulties in your vehicle, which can finally lead to a breakdown.

See also:  How long do car batteries last? (Solved)

The following are some warning signals to look out for if your alternator is steadily failing over time: As a result, how can you tell if your alternator is having problems?

The Warning Signs of a Failing Alternator

These warning lights are often shaped like batteries, however some may have the letters GEN (for generator) or ALt displayed on them (for alternator). In most cases, the triggering of these warning lights is based on how much power your automobile is consuming and whether or not your alternator’s output falls below a set threshold.

Headlight Trouble

A malfunctioning alternator is characterized by symptoms such as flashing, pulsing, or dimming headlights, among others. The alternator in your vehicle will not be able to adequately power your headlights if it is beginning to fail.

Other Electrical Problems

Power windows and power seats, for example, may begin to operate at a slower rate than usual or cease to function entirely in certain circumstances. A failing alternator may also result in the inability to operate your vehicle’s radio and internal illumination.


Your alternator is powered by a set of belts that run throughout your vehicle. If these belts are unable to move in the manner intended, they will produce excessive friction, which will cause the belt to become hot to the touch. This can result in a burning rubber smell similar to that of rotting rubber.

Smell electrical burning?

If you are smelling anything that smells like an electrical fire, it is possible that a belt is slipping and that it has to be adjusted. If tightening the belt does not eliminate the odor or enhance the power of your alternator, it is necessary to take your vehicle to a professional. In addition to diagnosing and repairing your electrical system, your localAAMCO Minnesota office can also service and repair your alternator.

Dead Battery

Battery failures in automobiles can (and frequently do) occur on their own. A faulty alternator, on the other hand, might cause your car battery to deplete and fail to recharge. If you find yourself having to jumpstart your car on a regular basis or if your battery dies, it’s time to have your alternator inspected. Check out this article for signs that your battery needs replacing.

Stalling or Difficulty Starting

Powered by electricity, the alternator in your automobile supplies electricity to the spark plugs that ignite the gas in your engine. If your alternator is beginning to fail, there may not be enough power in your spark plugs to start your automobile or keep it running for an extended period of time.

In the event that your vehicle stalls for no apparent reason, it might be a sign that your alternator is having problems. Reasons Your Car Won’t Start is a related article.


Unusual sounds emanating from your engine, in conjunction with some of the other symptoms listed, might indicate that your alternator is malfunctioning. Listen for whining, grinding, or rattling noises, since these might all be indicative of a malfunctioning alternator in your vehicle.

What to Do If Your Alternator is Failing

When it comes to diagnosing and repairing problems with your vehicle’s electrical system, AAMCO Minnesota has the best experts and equipment in the business. Including:

  • Alternator, drive belt, voltage regulator, starter, ignition switch, neutral safety switch, battery cables, and terminals are all included.

Create a service appointment with your local AAMCO Minnesota branch now to get the performance and safety of your alternator or other electrical systems checked out.

How Alternators Work

As we learned at the outset of this essay, a malfunctioning alternator will destroy a battery and cause you to lose your day’s work. The question is, why did the alternator malfunction in the first place? Having moving components, getting dirty, and being subjected to extreme heat and cold puts a strain on alternators. As a result, the internal components begin to wear down over time. Bearing failure is one of the most prevalent types of failure. The needlebearings that allow the rotor to spin freely within the stator might become damaged as a result of dirt and high temperatures.

  • Typically, an alternator with failed bearings produces a loud grinding noise when it fails.
  • Older vehicles equipped with generators tend to require significantly more maintenance than contemporary vehicles, but there is no hard and fast rule for how long an alternator will survive in a given situation.
  • There are a few simple methods you may take to determine whether or not your alternator is malfunctioning.
  • This light is typically symbolized by the sign of a rechargeable battery.
  • That is the voltage generated by the battery as it passes through the charging mechanism.
  • After all, the automobile may start, but as we discovered, the battery will quickly deplete and eventually die, and the electrical system will fail as well.
  • A voltmeter would be required to determine whether or not your car’s stator windings were malfunctioning in order to determine whether or not there was a problem.

This is referred to as a load test.

Connect the red lead (or wire) to the positive terminal and the black lead (or wire) to the negative terminal of the battery.

The voltage should be something in the neighborhood of 14 volts.

After that, switch on the headlights, air conditioner, radio, and everything else that requires electrical power to function.

Once again, the voltage should be in the range of 14 volts.

If this is the case, it is necessary to replace the alternator.

It is impossible for the alternator to work correctly if the belt is worn or loose.

A faulty belt is simple to repair and will not cost you much money, generally less than $20 in most cases. However, if you must replace the alternator, you have a number of alternatives. Continue reading to find out how to replace an alternator and how much it can cost you in the next section.


Automobile alternator difficulties are regarded to be one of the most significant types of automobile troubles. Because once they appear, the automobile might be left without electric power for an extended period of time, leaving it essentially worthless. The alternator will almost never fail you at the most inconvenient of times. Because it is generally a slow process, recognizing symptoms early on might make the difference between being able to drive safely and being stuck. This essay will hopefully assist you in identifying these issues in a timely manner, so preventing more harm and unnecessary expenditure.

Please visit this other post on alternator difficulties for more information on how to resolve alternator problems.


The alternator is a generator of alternative current that is powered by the engine’s power and pushed by a serpentine belt to keep the engine running. However, how can an alternative current (AC) generator give energy to an automobile when the car is equipped with a direct current (DC) installation? In short, a collection of diodes within the alternator (also known as the diode rectifier or diode bridge) converts alternative current into direct current, allowing the alternator to function as a direct current generator in its own right.

Because of the alternator, the old unreliable direct current generators (better known as dynamo machines) became obsolete in automobile electric power generation.

If you’re looking for a more in-depth explanation, check here for a fantastic explanation on Wikipedia.


When you see tell-tale indicators of alternator difficulty (flickering lights, the battery warning light illuminates, or anything similar), the easiest method to begin troubleshooting the problem is to measure the voltage output of the alternator. This is accomplished through the use of a multimeter. If you are experiencing mechanical alternator troubles, you do not need to use a multimeter (pulleys, bearings or else). Problems of this nature will express themselves in other, more evident ways in the future (grinding or screeching noise, snapping of the serpentine belt or else).

By examining the voltage output of the alternator, you will be able to determine with certainty whether or not the alternator is ‘guilty.’ The correct voltage output ranges from 13.5 volts at the lowest point to 14.5 volts at the highest point.

Click here to read a separate article on how to do an alternator voltage check on your vehicle, or visit our YouTube channel to view a video instruction on the subject.


Again, if you want to learn more about the lower-level alternator issues, please visit this other page.) The following are the most often encountered alternator issues:

1. Battery warning light stays on after starting the car

When you turn on the ignition, the battery light does not turn off automatically. Instead, it remains on at all times, completely glowing.

2. Dim battery warning light (barely visible but present after starting the car)

The battery light does not turn off after the car is started. As an alternative, it remains fully operational and illuminated at all times.

3. Battery warning light doesn’t come up at all

When you turn the ignition key in the ignition before starting the automobile, the warning light does not illuminate in any way. Additionally, there will be no warning light when the automobile is first started.

4. Grinding noise from the alternator

Something in the engine bay appears to have exploded with great force, according to the noise. Grinding, clanking, and shredding are all sounds that can be produced by a malfunctioning alternator.

5. Flickering head lights

Something in the engine bay appears to have exploded with great force, according to the sound. It is possible for an alternator malfunction to produce grinding, clanking, and shredding sounds.

6. Frequent burning out of headlight bulbs

The frequent and unnatural burning out of headlight bulbs that goes hand in hand with flickering headlights is a common occurrence. Use a multimeter to check the alternator voltage output if you have to change the light bulbs frequently (e.g., once a month). If the voltage output is excessive, replace the alternator. Changing the bulbs in your headlights is typically a simple task. Alternatively, you can read a separate essay on the subject by clicking here or see a video instruction on our You Tube channel by clicking here.

7. Anomalies in the electric and electronic systems

Powering electric and electronic equipment and components requires a consistent and reliable supply of power. Problems with the alternator might result in significant changes in the power supply to these components. This will present itself in a variety of ways, including the check engine light coming on for no apparent reason, gauges on the dashboard going berserk, electrical malfunctions, and so on. Perhaps the most frustrating aspect of this problem is that many drivers are forced to repair pricey electrical components for nothing when the alternator was the root cause of the entire problem.

8. Bad smell coming from the car battery (sulfuric smell, mostly resembles rotten boiled eggs)

If you notice a sulfuric odor emanating from the engine compartment, which smells like rotten boiled eggs, it’s a solid indicator that your alternator is having troubles. If the alternator is producing an excessive amount of voltage, the automobile battery (specifically the electrolyte) is the source of the foul smell. The battery acid begins to ‘boil’ within the battery, resulting in the release of these foul-smelling fumes. Because these vapors are combustible, this is a potentially deadly situation.

9. Screeching sound from the engine bay

This, in contrast to the grinding sounds, is a high-pitched sound.

The majority of the time, this is caused by a jammed alternator pulley or a highly worn out serpentine belt. Regardless of the situation, the high friction between the pulley and the serpentine belt is responsible for the screeching sound.

10. Snapping of the serpentine belt

Because the serpentine belt is under continual stress, this is a common reason. Not changing it in a timely manner, having a jammed alternator pulley, or having a damaged bearing are all major reasons of this situation. The most concerning aspect of this disease is that it can manifest itself at any time.

See also:  Heater core failure? (Question)


According to what I’ve seen, the following are the most common reasons of alternator problems:

Lack of maintenance

This is the first and most prevalent of all the reasons for a person to commit suicide. Alternators have their own servicing intervals that they must adhere to. Many drivers are unaware of this information, which might result in alternator issues. The service period is somewhat long (about every 200.000 kilometers), which may explain why so many people overlook it when they should. Maintenance consists in disassembling and cleaning the alternator, as well as replacing any faulty or worn out parts, and then reassembling the alternator.

Failure to pay attention to this period might result in the alternator failing completely, either physically (bearings, pulley, etc.) or electronically (electronic components) (lack or over-producing of electric power).

Installing low quality spare parts

If you perform maintenance on your vehicle with low-quality parts, you will experience problems again very quickly. If you want the repair to survive for a long period, you should always choose high-quality components. It will pay off since a well-done alternator service will ensure at least 100.000 kilometers (and maybe even more) of trouble-free driving without an alternator malfunction.

Mixing up battery poles when connecting a car battery

Especially among drivers who desire to do a car battery replacement on their own but lack prior training, this is a fairly typical blunder. Despite the fact that the marks on the battery connections and clamps are clearly visible, individuals nevertheless turn them around. This causes significant damage to the diode rectifier within the alternator in a large number of instances. In addition, it has the potential to cause harm to electrical automobile components. Please see this other post for information on how to properly connect a car battery.

Improperly jump starting a car

Switching jump wires can create alternator difficulties in the same way that it can cause problems with the car battery. It is possible to damage the diode rectifier again if the plus and minus wires (from the ‘donor’ car to yours) are switched back and forth. Even worse, you may end up causing harm to the ‘donor’ vehicle as well. Additionally, significant damage to other electric or electronic components may occur in this situation. For further information on how to properly jump-start an automobile, please see our separate article, which can be found by clicking here.

Power surges in the electric installation

In addition, any type of severe short-circuit or electric overload may result in an alternator malfunction. The diode rectifier and voltage regulator are particularly susceptible to this.

Over-tension of the serpentine belt

Prior to the introduction of automatic transmissions, this was a more frequent problem in vehicles with manual tensioning systems. These days, most automobiles are equipped with a self-contained belt tensioner, which ensures that when the serpentine belt becomes looser over time, the tensioner keeps it in position and tightly wound.

But if the tensioner wears down, it might lead to difficulties with the generator’s alternator (loose belt or worse, the belt can totally fall of the alternator pulley).

Broken or damaged wires

This occurs primarily in older vehicles as a result of the material fatigue of the electric installation. The connections on the alternator, as well as the connection on the battery terminal, namely the positive (+) connection, are the most frequently checked points on the vehicle. Another spot that should be checked is the connection between the alternator and the car’s ignition. When it comes to most automobiles, the primary positive (+) power line runs from the alternator to the starter before terminating at the car battery.

When recent mechanical work has been performed in the area of the alternator (such as belts, other pulleys, water pumps, or other similar items), it is possible that inadvertent damage to the wiring will occur.

Filthy or rusty contacts or connectors

Rust, dirt, and faulty connections are the bane of the electric appliances on the automobile, just as they are with all other electrical appliances on the car. It is important to ensure that all of your connections to the alternator are clear of corrosion and grime. If you see any of these symptoms, clean them as soon as possible since a weak contact might be a symptom of a more serious alternator problem (stator, diode rectifier or else). The alternator cables are often secured in place by a large plastic connection or by nuts or screws that are attached to the alternator itself.


Finally, I’d like to provide some suggestions for preventing alternator issues in the first place at the conclusion of this article:

Proper maintenance

Keep track of the alternator service interval and don’t leave it until the very last minute. This should be communicated to you by your mechanic or business. You may also check the service book to see when the last alternator check up was performed. My recommendation is to give close attention around every 200.000 kilometers. Also keep in mind that you are not required to wait this long. You may have your alternator cleaned and serviced prior to this period, which will help to prevent a problem and considerably extend the service life of your alternator in the process.

Make an alternator voltage check up part of your regular car check ups

Regularly monitoring the alternator voltage should become second nature, just as you would with other automotive inspections. Once a month should plenty, to be safe. Multimeters are not prohibitively expensive to purchase. A very good one will cost you no more than a couple of dozen Euros. In my opinion, it is a worthwhile investment because it will aid in the early detection of alternator problems, thereby saving you both money and time.

React to alternator problems immediately

When the first tell-tale indicators of alternator trouble arise, intervene as quickly as possible to avoid more damage. In addition to causing serious damage to the alternator, prolonged usage can also cause harm to the electric installation, electronic components, automobile battery, and other components. My key point is that if you put off fixing a minor alternator problem that is inexpensive and simple to remedy, it may evolve into a large and expensive problem.

As previously said at the outset of this essay, alternators are gems of automobile technology, having a built-in ability to withstand extreme conditions. If you take a little more care and attention, you can assure that your car’s electric supply will be reliable for thousands of kilometers to come.

7 Signs of a Bad Alternator to Watch Out For

If you’ve ever heard the phrase ‘alternator,’ you’re undoubtedly aware that it refers to a component that is critical to the operation of your car. However, what precisely does an alternator perform is unclear. Simply put, your alternator is responsible for keeping your car battery charged, which allows you to start your vehicle and operate electronic devices such as your headlights and radio. If you’re having alternator troubles with your automobile, you may notice that it won’t start or won’t remain on for more than a few minutes.

7 Signs of a Failing Alternator

When an alternator begins to fail, the voltage supplied to your electrical equipment becomes inconsistent, causing them to malfunction. The majority of the time, this manifests itself in the form of underperforming or overperforming equipment, such as headlights that are either too dim or too bright. Flickering lights or lights that erratically change from bright to dim and vice versa are other possible symptoms of this condition.

2. Dead Battery

After several years of usage, a dead battery is simply that: dead. Alternatively, you may have mistakenly left the headlights on all night, in which case the battery is simply that: dead. A dead battery, on the other hand, might be a warning that your alternator is not working properly at other times. An insufficiently charged battery can decrease the battery’s charge more quickly than normal if the alternator is not functioning properly when the engine is operating. Jumpstarting the automobile is one method of determining if the problem is caused by the battery or the alternator.

If, on the other hand, you jumpstart the car and it dies again shortly after, it’s possible that your alternator isn’t delivering enough power to the battery.

3. Slow or Malfunctioning Accessories

Slow or non-operational accessories are frequently caused by an alternator that is not giving enough power to the electronics in your vehicle. Whether you notice that your windows are taking longer than normal to roll up or down, or if your seat warmers are not working properly, or even if your speedometer and other devices start acting erratically, you may be experiencing an alternator malfunction. When the alternator isn’t producing enough energy, many contemporary cars include a priority list of equipment programmed into the car that informs the onboard computer which pieces of equipment to cut power to first.

4. Trouble Starting or Frequent Stalling

As previously said, having difficulty starting your engine might indicate that your alternator is failing to properly charge the battery. This implies that when you turn the key in the ignition, you’ll just hear a clicking sound instead of the purr of your engine when you switch it on.

If, on the other hand, your car stalls out regularly while driving, it might be an indication that the spark plugs aren’t receiving enough power from the alternator to keep the engine going.

5. Growling or Whining Noises

Cars generate a variety of strange noises, some of which are innocuous and others which might signify major mechanical problems. A malfunctioning alternator, which may be heard making growling or whining noises from beneath the hood, should be checked out by a professional as soon as possible. When the belt that rotates the alternator’s pulley gets misaligned or scrapes against the side of the pulley, a growling or whining sound is produced. In addition, if the bearings that spin the rotor shaft are failing, you may hear this sound.

6. Smell of Burning Rubber or Wires

A bad stench, such as that of burnt rubber or wires, might indicate that parts of your alternator are beginning to wear out and need replacing. It’s possible that the alternator’s drive belt will wear down over time due to the frequent stress and friction it experiences — as well as its proximity to the hot engine — as a result of its near proximity to the hot engine. Additionally, if your alternator is overworked or if it has frayed or broken wires, you may notice a burning stench that is similar to an electrical fire when you start your car.

The resistance created by damaged wires also contributes to the heating and emission of a foul odor, which is caused by the resistance to the flow of electricity.

7. Battery Warning Light on Dash

When the battery warning light illuminates on the dashboard, it’s typical for people to believe that there is a problem with the battery. But if your battery warning light is illuminated, it might signal that there is a problem with the rest of your vehicle’s electrical system, which includes the alternator. Alternators are engineered to operate at a set voltage, which is normally between 13 and 14.5 volts in most cases. If your alternator is failing, the voltage in your vehicle may fall below its maximum capacity, resulting in the appearance of the battery warning light on your dashboard.

As the alternator varies in and out of its intended voltage capacity, depending on the electrical demand placed on it by your car’s accessories (headlights, wipers, radio, etc.), you may see the battery warning light flashing on and off on a regular basis.

Alternator Service with a Smile

If you’re experiencing problems with your vehicle’s electrical system, it may be time to inspect the alternator. Firestone Complete Auto Care delivers high-quality servicing with the goal of ensuring that your battery and electrical system continue to function properly. Make an appointment online or stop by your local Firestone Complete Auto Care now for inexpensive, high-quality alternator servicing.

Leave a Comment

Your email address will not be published. Required fields are marked *