The Symptoms of a Bad Alternator, What Causes an Alternator to Go Bad?

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    Cars that are not equipped with alternators have low performance. When the car battery runs out, the car will experience a strike because the engine does not have electricity. Already imagine, right, how important is the car alternator?

    The questions are - What are the symptoms of a bad alternator?  and what causes an alternator to go bad? you will get an answer after you read the post.


    What is an alternator, its function, and how does it work?

    An alternator is a unit in your car that generates electric power.

    As the major unit of the car's charging system, It is bolted to the car’s engine. It is driven or rotated by a drive belt or serpentine belt. The alternator is connected to the car's engine using a belt or fan strap.

    When the car's engine turns, the belt will also set the pulley wheels on the alternator. The alternator is used by the alternator to produce electrical energy.

    One round of the engine will produce two pulley wheels on the alternator, and finally, the alternator will produce electric current from the stator coil. You do this by changing the engine speed into electrical energy by utilizing the electromagnetic working principle.

    Car Alternator

    Well, the way the alternator works is to convert mechanical energy into electrical energy.

    Car alternators utilize the principle of electromagnetic work and are the components that play an important role so that the electrical components in the car continue to function and have sufficient electrical power.

    The alternator works by charging the car’s battery when the engine is on. The alternator supplies additional electric power for the electrical systems in your car/vehicle.

    Then, the electric current is regulated by the IC regulator so that the electrical voltage generated is not more and can be used to charge electricity in the car battery. Quite understandably, isn't it?


    Essential Parts of the alternator

    As an vital part of a car engine, the alternator contains essential components that support its working principle as a producer of electrical energy.

    An alternator is made up of four main parts. These are the stator, rotor, Rectifier, and Regulator. 

    Then, what are the functions of the four critical components on the alternator? Here's the explanation.

    1. Rotors

    The rotor is the part that rotates inside the stator. Rotors function to produce magnetic fields. Inside, there is a collection of rotors or rotor coils that function to generate magnetic fields.

    The rotor is also known as the rotating magnetic core. It is also called the Flywheel of an alternator. This consists of a wire coil wrapped around an iron core. Rotors are the alternator’s moving part that has magnets moving around the iron plates of the stator.

    The movement of the rotor around the stator generates current called Alternating Current (AC). This will only happen through when the engine is already running. Once there is already an existing motion, the rotor and stator will work together to provide a charge for the car to move.

    2. Stator

    The stator is a copper coil arranged so that the rotor can rotate inside. The function of the stator produces an alternating electric current. In general, the stator has three independent coils that induce electromotive force (emf).

    The stator is a set of coils that are fixed to the alternator's shell. This is the one that provides a rotating magnetic field. The rotation of the magnetic field drives the rotating armature in the alternator.

    The stator is basically a guide in the car’s alternator system. 

    3. Rectifier (Output diodes)

    These diodes are also called the bridge rectifiers. These diodes convert the Alternating Current generated by the rotor to Direct Current (DC). AC cannot be used by the car, so it needs to be converted.

    The bridge rectifier has six diodes. Each pair of diodes is for one winding. One is for the positive, and the other one is for the negative half cycle.

    A rectifier also serves to change the alternating current induced in the stator coil. The rectifier also serves to hold the current from the battery to the alternator if the voltage produced by the alternator is lower than the battery voltage

    4. Regulator (Diode Trio)

    An alternator also has a voltage regulator. A voltage regulator has one output and two inputs. The inputs supply the field current and control voltage input. The output supplies the field current to the rotor.

    In this type of diode, one is used per alternator phase. This provides field current to the alternator regulator.

    The regulator, as the name suggests, is the one controlling the amount of field current input that is allowed to pass through and to the rotor winding. It is a component that functions to get a flat and stable current and voltage. This is because the electric current generated by the stator is unstable.

    In essence, the regulator functions to regulate the electric current that enters the rotor. If the electric current in the stator is less, the regulator will add electricity to the rotor, but if it is excessive, the regulator will reduce the amount of electricity that enters the rotor.

    Well, thus, the voltage and electric current generated by the alternator will always be stable and constant.

    alternator parts of the car

    After knowing the alternator parts of the car, you certainly understand that caring for the electrical conditions in the car is essential.

    In caring for a car alternator, there are some important things to consider.

    First, avoid modifying the lights with variations that require too much power supply. Second, you should also avoid installing audio systems that are out of standard.

    If you want to upgrade the audio and lighting system, it means you also have to upgrade the electrical partitions in your car.


    Is the alternator broken prematurely?

    The alternator is one of the parts or components that can be said to be very vital to the car.

    The useful life of the alternator in general and usually from the new condition is up to 7 years or about 100,000 to 150,000 miles.

    If you have exceeded the maximum usage limit will make the performance decreases and also decreases.

    The following are some of the causes of alternators breaking down faster than their normal use life:

    1. The process of installing accessories or attachments with a large load
    2. The rectifier diode on the alternator is disconnected from the regulator IC. This results in the current to be given and produced by the alternator to be reduced
    3. Use cut-outs in the Out External Voltage regulator section.
    4. The relationship between carbon brush and rotor slip rings is less than optimal and also not good. This can make your car's alternator drop quickly, and of course, it will hamper the electricity supply to the rotors on the alternator.

    What are the symptoms of a bad alternator?

    Your car's alternator is important for it to run well. So, what signs do car owners need to look out for to know if they have a bad alternator? The following are symptoms that an alternator is failing:

    battery indicator lights

    1. The battery indicator lights up

    Turning on this light indicates a failure in electricity or the battery does not charge completely. The indicator lights in your dashboard are your first sign that something is wrong.

    Do not rush to assume the battery condition is weak. Because the output of the alternator causes, the flame indicator lights is not as it should be.

    2. Headlights are flickering or dim (Headlamp Dims)

    The alternator is the one giving power to the headlights. If the headlight is not working properly, this means the alternator is struggling to perform.

    This dim Headlight indicates that the electricity supply from the alternator is weakening. The small amperage supply must have made the lights dim.

    3. Damaged or Dead battery

    ​There are times when the car's batteries fail. A failing alternator, though, can cause your car’s batteries to die. This happens when the alternator fails to recharge the drained battery.

    Alternator system failure is sure to have an impact on battery life. What you need to know is to distinguish the alternator or battery failure.

    The trick is if your car dies and due to weak electricity, try your battery jumper and start the vehicle then immediately unplug the jumper cable. If the car continues to turn on, make sure your battery is damaged. But if your car's engine slowly turns off, it's almost certain this is damage to the alternator system.

    4. Strange noises

    A lot of things can cause unusual noises in the car. A failing alternator is one of those reasons. An alternator failure can cause some bearings to fall out. This makes the rattling sounds inside the car.

    5. Stalls or has difficulty starting

    Your car needs gasoline to run. It doesn't solely run on gasoline, though. The car also needs electricity to run.  Your car’s alternator provides power to the spark plugs. This will ignite the gasoline in the car’s engine.

    When the alternator fails, there is not enough power for the spark plugs to keep the engine running. This results in the car stalling or difficulty starting.

    6.Other electrical failures

    When the alternator fails, all other systems it powers up also fails. These include the air conditioning system, power locks, dashboard lights, power windows, and sometimes even the car radio.


    Understand some of the symptoms if the alternator becomes terrible. Do not let the vehicle's electrical system only supported by batteries.

    If you only use batteries, the engine can not be started because the supply of energy to the battery from the alternator is not regular. 

    What causes an alternator to go bad?

    Defective bearings

    An alternator revolves on a high-precision needle bearing. These bearings are silent when they rotate. If the bearing is defective, the alternator produces loud rumbling noises.

    The noise is from the bearings falling apart.

    Worn belt

    As said earlier, an alternator uses a serpentine or rotating belt to generate power. Over time, this belt can become loose and worn out. If you see that the belt nearest the pulley is fissured or glossy, this means it needs replacing.

    Failing Diodes

    Each diode supplies the alternator with varying levels of power. As time passes, these diodes can break down. When a pair of diode fails, the other working pairs will bear a greater share of current capacity.

    If the pair of diodes still provides 1/3 capacity of current, the car will still run. If all three pairs of diodes fail, the car’s electrical functions will not be able to activate.

    A leaky diode is another type of diode failure. A leaky diode can also allow current to drain out of the battery. This is through the alternator. This happens even when the vehicle is not being driven.

    Insufficient field voltage

    Your car needs to have 12 volts of field voltage to produce electricity. Low volts of field voltage will diminish the performance of the alternator. 

    Other reasons why an alternator goes bad are faulty wirings, improper fitting of a wiring harness, and connection to the power problems.


    Sometimes, when there is a misdiagnosis, it can also make the alternator go bad. There are times when the alternator is not the problem but the surrounding system. It was just misdiagnosed. The improper handling of an alternator by an examiner can do more damage than good.

    Now you know what the symptoms of a bad alternator are, here is - how to test Your alternator for your car.

    To test if the car has enough voltage, use a voltmeter.

    If you see some of the signs stated above in your car, it is best to have it checked by a proper service and repair center as soon as possible. This will not only save your car but your finances as well.

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