Alternator: The Ultimate Guide

Car Alternator Banner

When talking about a vehicle engine and the various electrical accessories, the thing  alternator always have something to do.  Why is that so? The alternator directly or indirectly affects the operation of different systems in an automobile. In the absence of alternator, the battery would not charge. The engine would have trouble starting, and the vehicle’s electrical systems would collapse.

The alternator became a standard automotive component many decades ago. It has undergone many transformations over the years, of course. Today, the component is a lot more efficient and powerful. You will also find it in every vehicle that uses an internal combustion engine where it works the electrical parts and systems.

In this ultimate guide for alternator, we bring you everything there is to know about the alternator- from how it works, the parts that make it, the different types of alternators to the signs of malfunction. You will also get to know how to test an alternator for problems and also give help for you restore the alternator’s function in the event of failure, information on how to repair or replace it.

Car Alternator Definition And Function

Car Alternator

What is an alternator in a car? It refers to the component that produces electricity from the motion of the crankshaft. The alternator usually bolts to the engine block, at one end. A pulley and belt system connects it to the crankshaft, from where it gets the mechanical energy to spin.

You can recognize the car alternator by its appearance. It’s approximately the size of an average coconut and usually features an aluminum housing. There are vents on both the alternator’s front and back that help to cool it. On the front of the alternator, a shaft sticks out and attaches to a pulley. The pulley then has a belt looped around it. On the side are the terminals for the different circuits.

Shows example of alternator of a car
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Alternator Function

What does a car alternator do? The alternator function is similar to that of a conventional generator: to convert mechanical energy to electricity. The electrical energy it produces powers several accessories in an automobile. These include lights ( both interior and exterior), heater, the instrument panel, windshield wipers, the car radio, and more.

Apart from powering the car’s electrical systems, the alternator charges the battery so that it’s ever ready to do its work. That’s why the battery starts the engine every time you need it to, and why you never have to charge it outside the car. The vehicle then appears to have that never-ending supply of electric power.

An alternator only produces electricity when your car’s engine is running. It supplements the battery at that time, and for a reason. On its own, the battery can only power the electrical systems for a limited period. And if it did that in the absence of an alternator, it would drain completely and become unusable.

Alternator Working Principle

Let us now look at the operation of the automotive alternator- how it works to produce the much needed electric power in a vehicle. Also, why the component is different from the normal generator.

The alternator in your car primarily comprises a stator and rotor. Put simply, a stator is the stationary part of the alternator that consists of three different wire coils. The rotor is the part that spins. It also features coil wires but which enclose a magnetic core. This is what happens in the automotive alternator that leads to the production of electricity.

  • When the engine starts, it rotates the crankshaft
  • The crankshaft spins a pulley to which a drive belt is connected. The belt turns several pulleys, among them the one that works the alternator
  • When the alternator pulley rotates, it causes a rapid spin of the rotor
  • The rotor consists of coil windings around a magnetic core. When the alternator is in operation, direct current from the battery flows through the coil wires to create a magnetic flux around it
  • As the rotor spins, the magnetic flux cuts the stator coils and by electromagnetic induction causes a flow of current in the stator windings. The intensity of the current depends on the speed of the spin and can be controlled, as we will see later
  • This current is alternating and needs to be rectified before it can be used to power the various components in the car or truck
  • A rectifying circuit consisting of diodes and other parts works to convert the AC to DC, or direct current
  • A circuit directs the alternator electric power to the battery to charge it, and another to the various electric systems
  • The components and systems that need electricity come to life, or do so when you switch them on. The battery also charges and its electrical energy restores. The battery’s power is conserved to start the engine the next time and to serve the various demand for electric power when the alternator isn’t operating.
How alternator works

Alternator History

The alternator principle was discovered way back in the 1830s. A few decades later in 1891, the first industrial application of the alternator generator happened. Technology evolved rapidly, and by 1960 it became standard practice to build cars with an alternator.

Before that, vehicles used generators to power different electrical parts. But these were not powerful or efficient when it came to producing the desired current and voltage. As technology advanced, vehicles had more accessories being incorporated into their electric systems. With the increase in power demands came the need for a different type of power generating unit.

Within no time, manufacturers began to use alternators instead of generators to power the various vehicle electrical components an circuits. These were capable of producing higher voltages and currents at lower speeds.

The use of alternators has continued to this day. Every modern automobile comes with an alternator as the power generator. What only keeps improving is the design, materials, various alternator parts, and other aspects of the device. The working principle hasn’t changed.

De automotive alternator is made up of many different parts, all working together to ensure the device performs its function. When each alternator component is operating correctly. and at its optimum level, the battery charges fully. The different electrical systems will also work without failing. In the next chapter, we take a look at these alternator parts that enable it to function.

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Alternator Parts/Components

parts of alternator

The alternator has come a long way. Since the time it became a common car component in the 1960s, a lot has been done to make it better. The car alternator of decades ago was a simple device, but the modern one is a complex piece of equipment. It consists of several parts, each with a specific purpose to serve.

Alternator Parts And Function

1. Stator

Image of Stator
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This is the non-moving part of the alternator that surrounds the spinning rotor. The stator is circular in design and usually consists of three different wire coils wound around a core. The core itself comprises either iron or steel pieces. These increase the magnetic effect that’s needed to induce an electric current. The stator coils produce what’s known as three-phase power. This design comes with benefits as we will see shortly.

The stator changes the mechanical movement of the rotor to electricity. When the magnetized rotor coil spins, it creates current in the stator windings through electromagnetism. Due to the alternator design, the current that it produces changes direction many times in one second. It needs to be rectified before being fed to the various vehicle circuits.

2. Rectifier

Image Sample of a Rectifier
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Connected to the stator, the rectifier consists of a series of diodes. The diodes are arranged in such a way that they allow current to flow in one direction only. The work of the rectifier is to convert the alternating current that the alternator produces into direct current. As we saw earlier, one of the functions of an alternator is to charge the battery. That cannot happen with the AC that changes directions every time, and the reason for the rectifier.

Many other electrical parts of a vehicle also cannot use alternating current. Besides that, there’s the safety hazard that AC presents. The rectifier is, therefore, one of the most important parts of alternator assembly. Its presence serves more than correcting the direction of flow of the current. In a three-phase power alternator, 6 diodes work together to rectify the current.

3. Rotor

Image Sample of a Rotor
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The alternator rotor assembly holds several components, unlike the stator. It comprises of a magnetic core, coils wires wound around it, slip rings, end bearings, and the brushes. The rotor is the spinning part of the alternator. It’s driven by the pulley that attaches to it and which spins when the engine is running. The components on the rotor shaft include:

  • Cooling fan- In the older motor vehicles, the cooling fan was placed outside of the alternator, on the rotor shaft. As its name indicates, the fan prevents the alternator from overheating, as can happen when you’ve been driving for a long time without stopping.
  • Brushes- the alternator brushes are made from carbon and serve to convey current to the rotor coils. Alternator brushes are tensioned by special springs to make stable contact with the slip rings.
  • Slip rings- the slip rings are circular pieces of copper on the crankshaft. Just like the carbon brushes, their work is to pass current to the rotor coil windings. The ends of the coil attach to the rings.
  • End bearings- these support the rotor shaft and allow it to move freely. They are crucial to the normal operation of the rotor and, therefore, the whole unit.

4. Voltage Regulator

Image Sample of Voltage Regulator
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The alternator regulator controls voltage output. It does so by varying the current that flows from the battery to the rotor windings. When the output voltage decreases, it suppliers a higher amount of current and restores the output. When the alternator voltage increase, the opposite happens.

That way, the regulator ensures a steady voltage level. The battery remains protected from overloads or irregular charging, and its lifespan increases. Other electrical circuits are also kept safe from higher voltage levels which could result in damage. In the older vehicle models, the regulator mounted on the fender. In the newer ones, it’s an internal alternator component. Some use the vehicle’s computer system to ensure the right output at the alternator terminals.

5. Pulley

Image Sample of a Pulley
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De pulley is situated on the outer part of the alternator but connected to the rotor shaft.  The drive belt system runs around it, providing a means for the crankshaft to spin the alternator rotor. As long as the pulley rotates, electric power is produced in the stator coils. The older vehicles have a simple belt that ran from the alternator to the crankshaft pulleys. The modern ones feature a serpentine or drive belt.

6. Housing

Image Sample of the Alternator's Housing
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The list of alternator parts cannot be complete without a mention of the housing. This is the case that encloses the internal components. It’s usually made of aluminum to make the alternator both lightweight and rust resistant. The housing is usually vented to increase the flow of air and facilitate cooling. That’s because heat is produced as the rotor sound at high speeds.

Other parts that are in a way connected to the alternator but not directly include the following.

  • The alternator belt- this goes around the alternator pulley all the way to the one attached to the crankshaft. It drives the alternator whenever the engine is running
  • The brackets- these allow you to mount the alternator to the engine block. There’s the rigid bracket and the type that allows for adjustment. The adjustable bracket allows for the tightening of the pulley belt. It’s used in the vehicles that don’t come with the belt tensioner
  • The belt tensioner- it forms part of the alternator mounting brackets. You use it to tighten the drive belt to the required level of tension
  • The alternator connections- these allow current electricity to either leave or go into the alternator. There are the leads from the battery to the alternator and others that supply current from the alternator to the necessary destinations.

Now that we have looked at the alternator parts and operation, let’s see about the types of alternators: the topic of the next chapter.

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Alternator Types

Aternator Types

Generally, alternators vary in design, method of operation, and other aspects. Automotive alternators don’t present many differences, though, and are almost similar for different brands. Other than the automotive industry, these pieces of equipment can be found in various fields of application.

Power generation plants, for example, use high-output alternators to produce electricity. Different industries also use alternators to power various process. Because of the different uses, alternators vary depending on the application. The differences occur in the design, working action, size, and so on. In this chapter, we will look at the different alternator types including those that are not used in automobiles.

Alternator Classifications

Alternators come in many types but which can be grouped on the basis of many aspects. These include:

1. According To Application

Marine Application Alternator
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  • Automotive alternators- These are found in modern cars, mostly those that use internal combustion engines. They’re compact pieces of equipment that ensure a vehicle’s electrical systems are powered at all times
  • Marine alternators- Refer to the alternators for marine applications. These have the characteristics suit their environment such as parts that can withstand salty conditions. They’re designed to produce 12v to 24v depending on the power requirements
  • Diesel-electric locomotive alternators- Used in the diesel-electric transmission locomotives to supply the traction motors with electric power
  • Brushless Alternators- The brushless alternator uses a unique design that doesn’t require an outside excitation current. The exciter assembly mounts on the rotor shaft. These alternators are low-maintenance since the number of wearing parts is greatly reduced.

2. According To Design

  • Salient Pole- This type of alternator features a magnetic pole that projects out of the surface of the rotor. These alternators operate at low speeds, in the range of between 150 and 600 rpm. They’re, therefore, mostly hydraulic driven.
  • Cylindrical Rotor- This one doesn’t use a projecting rotor surface. Instead, the rotor is long and small in diameter with four poles and higher. The air gaps are uniform. The cylindrical rotor alternator type is a high-speed power generating unit. It runs at speeds of between 1500 and 300 rpm.

3. According To Working Principle

  • Revolving Armature- Designed to have the armature rotate in a stationary magnetic flux
  • Revolving Field- The armature remains stationary while the magnetic field revolves. The output can be applied to the load directly and slip rings or brushes are not necessary

4. According To Power Output

  • Single-Phase- The stator windings in this type of alternator are arranged in series, firming a single wire coil circuit
  • Two-Phase – The stator coil in this alternator consist of two or more separate single-phase windings
  • Three-Phase- The stair is made up of three single-phase coil. It’s the standard design for the automotive alternator

5. According To Rotation Speed

Image Sample of Turbo Alternator
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  • Turbo- These are connected to turbines and are high-speed alternators that produce huge amounts of power. Turbo alternators often operate at 3000 rpm and higher. The rotors of turbo alternators are mostly cylindrical
  • Low-Speed- Operate at low speeds of less than 1000 rpm, unlike the turbo-alternators. Low-speed alternators are mostly hydraulic driven

Alternator Vs.Generator: What Are The Differences?

Image Sample of difference between Generator and Alternator

Generator Vs. Alternator

This Youtube video explain the diffence between the Generator and Alternator

The alternator is different from the usual generator in a number of ways.

First, a generator produces direct current while an alternator outputs an alternating current. Second, generators feature a rotating armature inside a stationary magnetic field. An alternator, on the other hand, mostly utilizes a spinning magnetic field inside a stationary ring of coil windings.

Another difference between an alternator and a generator is in the amount of current each produces. The current at the alternator terminals is usually much higher. Generators mostly feature a single coil of wire while an alternator comes with three different coils. The three-phase design results in three times more electric power.

The efficiency of an alternator is also higher. It produces higher voltage and current levels at lower rotor speeds. In terms of size, the alternator is usually more compact when compared to a generator of the same design and power rating. Alternators are also lighter, which makes them suitable in most situations. Apart from that, they’re cheaper, and therefore economically sound to acquire.

De Automotive Alternator

For the reasons described above regarding the alternator generator differences it’s obvious that the alternator offers more advantages. It produces higher voltages at lower speeds and more current. Alternators can also be small-sized while still maintaining efficiency and power. For these reasons, this device has been the preferred power generating unit in automobiles.

Unless your car or truck was manufactured prior to the 1960s, it will have an alternator under the hood. These electricity generators are efficient and high-performance. But they have a lifespan. In the long run, they develop problems, and you may need to replace them. Let’s see that in the next chapter.

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Bad Alternator Symptoms

Shows Bad Alternator Symptoms

The alternator is one of the key components of an automobile. It helps to power the electrical systems and keep the battery ready for temporary power demands. But then, the alternator assembly parts that spin. These keep wearing out every time you set the engine running.

Eventually, it reaches a time when the wear is so severe that the working of the alternator becomes hampered. When that happens, symptoms start to show. The signs of alternator issues often begin with small warnings which intensify as time goes by. In the long run, the alternator may even stop working.

Apart from the moving components, there are the electric circuits of the alternator can malfunction. This is a common problem with the rectifier and regulator. If not addressed, circuitry issues can cause the whole power generating unit to fail. Taking action early can help avert alternator failure and save you a lot on replacement costs. Therefore, always be on the lookout for these signs.

1.Dashboard Warning Light

Shows image of Dashboard warning Light
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Most cars will have a dashboard light to indicate various issues. The light icons vary from one car make to another. It can be a battery sign in some and a GEN or ALT in others. In the older models, the sign for alternator problems is usually GEN. It means generator, the name that the alternator was known by in the past years.

What could cause the dashboard warning light to come on? The alternator maintains a voltage of between 23V and 14V. If there’s a malfunction, the voltage can either exceed the higher value of go below the lower one. The vehicles computer system picks the discrepancy, causing the dashboard warning sign to light up.

2.Unusual Alternator Noise

Strange noises under the hood can indicate various problems. One of them is a bad alternator. If the noise is coming from the alternator, you should suspect several possible scenarios. The issue could be worn out bearings, especially if the noise resembles that of grinding metal parts. A squealing sound could be a sign of a broken alternator belt. A bushing that has worn out can also cause a bad alternator sound.

3.Stalling Of The Engine

In the modern automobile, a fuel injection system replaces the carburetor. To operate at an optimum, the direct injection system requires adequate amounts of electric power. A failing alternator will cause the supply of electricity to diminish, and the results are felt at the engine. Sometimes, the vehicle may even fail to start. You may hear the normal clanking and relay noises when you turn on the ignition key, but silent immediately after.

4.Headlight Problems

Healight Damage
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The alternator supplies the power to light up the headlights. When it fails, the power that it sends to the electric system will be unstable. The lights will then either dim, flicker or go excessively bright. Often, the headlights will start with dimness that brightens as the engine (and the alternator) picks up rpm. Should that happen, you likely have a bad alternator. The problem could be the regulator that’s malfunctioning and unable to correct the alternator output.

5.Electrical Problems And Slow Accessories

Many vehicle parts and accessories depend on the alternator for the electricity to power them: windshield wipers, rear window defroster, power seats, windows, radio, and others. If any of these start to operate slowly, the problem is likely the alternator that’s not producing the required voltage. In some cases, one or several accessories will operate well but fail when you switch on another. That signals low electric power and a failing alternator.

6.Dead Battery

When the alternator has worn out, it doesn’t charge the battery to its full capacity. The battery still has to produce power, though. This leaves it completely drained of charge. Because there’s little or no charging taking place to restore the battery’s power, it reaches a point where it ceases to work. One of the first signs for this is an engine that cannot start, among other failures. You may then need to replace both the alternator and the battery.

7.The Smell Of Burning Rubber

Image of Burning Pulley
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You will notice this when the pulley belt heats up excessively and produces a smell. It often indicates a badly positioned belt that generates too much friction. It could also be a drive belt whose movement is hindered in one way or another. While not every smell is a symptom of a bad alternator, it’s a signal that you shouldn’t ignore.

Bad Alternator Q & As

  • What Causes An Alternator To Fail?

There are many reasons for a malfunctioning alternator. One of them is worn out parts that affect the normal functioning of the unit. When the spin of the alternator rotor is affected, many things can go wrong.

A drive belt that doesn’t spin the alternator rotor can also cause it to fail. It could be a loose belt that slips off or one that’s wrongly placed in the pulley groove. Slipping alternator belt symptoms include strange noises under the hood. And in the worst of cases, an alternator that doesn’t power a vehicle’s electric systems at all.

  • Can You Drive A Vehicle With A Bad Alternator?

Yes, you could, but only for as long as the battery can power all the electric systems in your car. Because the battery can only do that for a short time, it wouldn’t be a good idea to drive while your alternator malfunctions. The risks of driving with a bad alternator include the car stalling in the middle of nowhere.

Bad Alternator Vs. Bad Battery

Both the alternator and battery work hand in hand. The alternator keeps the battery going and the battery chips in when the alternator isn’t producing power. If either of them fails, the electrical systems in a vehicle suffer. The engine may not start, which then would mean an alternator that won’t run.

How can you tell the one that has failed? The first step would be to observe the symptoms. If the alternator is old and producing strange sounds, it could be the problem and not the battery. The same case if the drive belt is broken or loose and not spinning the alternator pulley. For battery, you would have a reason to suspect its failure if the car doesn’t start. But then, there could be other reasons for the stator problem.

So, how do you tell if it’s the alternator that has broken down? Or what tests do mechanics carry out if you take your car to them for alternator repair?  That’s the topic of the next chapter.

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Alternator Troubleshooting /Diagnose

The symptoms of a bad alternator indicate something is wrong with the unit. However, you may not know what part has failed. Performing tests to determine the problem is then necessary. Troubleshooting the alternator allows you not only to pinpoint the issue but also find out the extent of the damage. In this chapter, we will discuss the way or ways to do that. Let us start by looking at how to test alternator function and operation for issues.

How To Test An Automotive Alternator For Voltage Output

For this test, you need a voltmeter. This tools measures measure voltages. You can use a multimeter if it’s the only tool that’s available. It also reads voltage levels among other measurements

Note: Never disconnect the black cable of the battery during the whole testing process. Modern automobiles use a computer system to control the alternator voltages. Disconnecting the negative cable would remove the battery buffer and send the signal of voltage loss. That would cause the car computer to react by increasing the alternator voltage many times, damaging the electrical systems instantly. In the older motor vehicles, that may not be a problem.

Show image of disconnecting black cable during whole testing process
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The Testing Procedure

  • You will need to prepare the voltmeter first. If it has been lying unused for long, the batteries might be weak. Replace them. Next, rotate the knob until it points to the DC position. Ensure the reading on the display is 0.000 volts. If using a multimeter, set it to 20 volts DC
  • You will need the alternator running to carry out this test. That in turn, requires that the battery be in good condition. Start, therefore, by checking the battery to ensure it isn’t damaged
  • To test the battery, turn off the car’s engine and open the hood
  • Connect the voltmeter’s red lead to the positive terminal of the battery and the black one to the negative terminal.
  • If the battery indicates 12.2 volts or more, its condition is good enough, and you can use it to test the alternator. If the battery’s voltage is lower than that, find another one. You may also choose to test the alternator using a different means.

Now, onto the alternator testing process

Alternator Process Testing
  • Start the engine and rev it up to 2,000 rpm. This will start the alternator and spin it to a high speed
  • Check to see that the serpentine belt that drives the alternator is adequately tight and not worn out
  • With the engine running, retest the battery. The voltage should now read between 13 and 14.5 volts under varying rpm, If the voltage doesn’t fluctuate between these two values and remains constant, the alternating isn’t performing correctly. Also if it drops lower than this
  • Repeat the test with a few of the electrical accessories such as the radio on. If the voltage goes above 13V, the alternator is working properly and charging the battery as it should.

This is the idea behind the battery and alternator tests:

Testing the battery helps you to determine if it’s in good condition. If it isn’t, you cannot get the right results when troubleshooting the alternator for issues.

Testing the alternator for voltage output helps you to tell if it’s producing power. When the alternator is running correctly, it should charge the battery automatically. You can pick this as an increase in voltage at the battery terminals.

When you switch on the vehicle accessories that use electricity, you put a strain on the alternator. It should react by increasing the amount of power it produces which again reads at the battery terminals as increased voltage.

If the voltage remains constant even when the engine is running, it means the alternator is producing little to no power. And if it drops when you have increased the demand for electricity by powering up an accessory, the alternator is weak or the regulator circuit is faulty.

Sample Image of Testing the Alternator Diodes
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The alternator diodes change AC to DC. When they malfunction, the alternator leaks AC voltage into the different circuits. It results in damage to different accessories. The battery could also get damaged before its time and a host of other problems.

To test the diodes, set the engine to more than 1200rpms and set the voltmeter to measure AC voltage. The display should read 0 volts. If there’s an AC leak, you will catch that in the voltmeter readings.

Other Ways To Diagnose Alternator Problems

Apart from using a voltmeter or multimeter, there are other methods to determine whether the alternator is functioning correctly. They include:

  • Listening In For Unusual Sounds

Turn on the engine so the alternator comes into operation. While the engine is running, use a rubber tube to listen for any noise that could be coming from the alternator. A problem with the bearings often manifests as a grinding noise. If it’s a squealing sound, you could be having a loose belt.

Switch on a few accessories, one at a time. If the alternator is failing, the noise will increase with every additional accessory that you switch on. A buzzing radio indicates an alternator whose rectifier is isn’t working properly, leaking voltage into the system.

  • Using The Alternator Gauge

If your car has the voltage or amp gauge, you can use it to troubleshoot the alternator. Rev up the engine to 2000 ROMs. Turn on a few of the car accessories that are powered by the alternator. Check the gauge for the volt readings. If you notice a decrease in the voltage or amperage, the alternator isn’t performing as it should. If there’s an increase even when the accessories put a strain on the alternator, then there’s no issue with it.

  • Physical Observations

A frayed or cracked belt is usually the culprit when the alternator doesn’t produce the required power. It could also be that the belt isn’t tight enough. A loose drive belt will not turn the pulley as it should. Check the belt tensioner, which is often the cause of this alternator problem. Its spring could be broken.

After you’ve carried out tests and inspections on the alternator, you will likely find the problem with it. If it appears to be in good condition, other issues could be causing the charging and power supply issues. These include loose, frayed, or corroded battery cables, bad communication between the computer system of the car and the alternator regulator. It could also a blown fuse among other problems.

Depending on the type of damage, you may choose to carry out repairs or replace the alternator. Most of the time, a damaged or malfunctioning alternator will require to be discarded. How do you carry out an alternator replacement? That’s what we look at in the next chapter.

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Alternator Replacement

How To Replace An Alternator

You just checked the alternator and found it to be too defective to fix. So you obtain a new one, and you’re all set to install it. Where do you begin and what’s the procedure to ensure the correct mounting and connections? While alternator replacement can be a DIY task, knowing the steps to follow is crucial. Doing it the wrong way can affect many functions in your car, seeing that the alternator powers the electric systems.

Should you decide to carry out the replacement yourself, this is the process, from removing the old alternator to bolting up the new one.

Removing The Old Alternator

How to Remove Old Alternator
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  1. Disconnect the battery. This is important for safety reasons. To do that, use a socket or wrench to loosen the bolt that holds the negative terminal cable. You do not need to remove the positive cable.
  2. Locate the alternator. If you have to jack the vehicle, ensure that you do so safely, with the car parked on a flat surface and the parking brake engaged.
  3. Remove the main power cable. This is the power line that runs all the way from the alternator to the battery. Use a wrench to loosen up the bolt that secures the cable.
  4. Using a screwdriver, release the clip that holds the alternator wiring harness. Safely clamp the wire out of the way.
  5. Remove the pulley belt. If the one in your car features a belt tensioner, use it to loosen the belt around the alternator pulley. If it uses the mounting brackets to tighten the belt, you can utilize that to ensure the belt comes off the pulley easily.
  6. Check the pulley belt for signs of wear. If it appears run down and cracked, this is the best time to replace it.
  7. Remove the alternator from its mounting bracket. It may present some challenges but don’t force it. instead, take your time.

You now have the alternator wiring disconnected, the belt off, and the alternator itself off the mounting area. You can now prepare to install the new one.

Mounting The New Alternator

Mounting the Alternator
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  1. Before installing the new alternator, place two- new and old- together to see if they are similar. The size, design, mounting slots, and the cable connectors should match.
  2. Next, slide the new alternator where the old one was, taking care not to damage the drive belt or wires while doing so.
  3. Slip the mounting bolts down the slots on the alternator all the way to the mounting bracket.
  4. Using a wrench, tighten the bolts. If your car uses an auto-tensioner, tighten the bolts fully. Otherwise, do so slightly so you can later slide the alternator to achieve the right belt tension
  5. Loop the belt on the alternator pulley. If it’s the winding type, ensure you route it correctly. You can use the car’s manual if unsure.
  6. Tension the drive belt using the appropriate means for your type of vehicle.
  7. If you were yet to tighten the bolts, do so at this point
  8. Connect the wire harness and the power cable. Ensure tight connections.
  9. Connect the negative terminal cable back to the battery
  10. Lower the vehicle if you had jerked it. Close the hood and text the new alternator.
Closing the hood and text of the new alternator
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Alternator Replacement Q & As

  • How Long Does It Take To Replace An Alternator?

It varies depending on one’s skills and experience level. The duration can be as little as an hour for those who have done it before and two hours or more for the unskilled. Here, we are considering when you do it yourself. If you take the car to a repair shop, the alternator replacement time may vary greatly. That’s because other factors will come into play. You may have the car in there for even a whole day.

  • How Often Should An Alternator Be Replaced?

Generally, after every 100,000 to 150,000 miles. But mechanics will tell you they replaced an alternator that had a mileage of slightly below 100,000 miles. The best idea is for you to stay alert for the signs of wear and damage. That way, you will replace the alternator on time.

  • How Much Does It Cost To Replace An Alternator?

Again, that depends on the car model and year of make. On the alternator brand too. The cost of a new unit ranges from $200 to 300. Add to that labor costs for the installation, which varies from region to region and from one mechanic to another.  Choosing to carry out the replacement yourself can save you a lot.

  • Do Alternators Come With A Pulley Installed?

Some do, some don’t. If the type you have for replacement comes with one, it should be compatible with the drive belt. You don’t want to experience pulley spinning issues just after installing the new alternator. If it doesn’t, you may have to use the one on the old alternator.

Replacing an automotive alternator shouldn’t be a challenge. You do not need any special skills or fancy tools. To ensure everything goes well observe the safety precautions. Put on protective gear, and keep rags on the ready. Always disconnect the negative terminal of the battery before you can start working on the alternator. And if you’ve been driving for long, allow the engine to cool first.

What if the alternator isn’t high mileage and only a few parts have become faulty? Then you may consider fixing those, especially if the components are reparable. Let’s see about that next.

Hoofdstuk 7

Alternator Repair

Just like many other components in a motor vehicle, the alternator contains parts that can be repaired. That means you do not have to replace it every time you detect a malfunction. Sometimes, you only need to find the cause of a fault and fix it.

There are even alternator rebuild kits which can help you restore the alternator condition at a lesser cost. And if you choose to carry out the repairs or rebuild yourself, you end up spending only a small amount of money.

Before you can begin fixing a bad alternator, you need to pinpoint the faulty part first. That involves carrying out the tests and inspections explained in the previous chapter. Once you know what requires fixing, you can go ahead and do it.

Common Alternator Problems And How To Fix Them

There are the alternator components that will often break down or wear out. These require fixing rather than consider the costly option of replacing the whole unit. They include;

Image Sample of Loose or Worn out Pulley
Source :

1. Loose or worn out pulley belt- this could be causing unusual buzzing or squealing sounds. To find out if this part is faulty, you only need to open the hood and inspect it. A loose serpentine or V- pulley belt requires tensioning. Depending on the make and model of your car, use the automatic tensioner or slide the alternator along the bracket. Only ensure that the belt is neither too tight nor too lax. If the problem is a worn out or broken belt, replacing it could be the only solution.

2. Faulty diodes- if one of several diodes are not working, there will be a leak of the AC voltage. As we saw earlier, you can test for leaking voltage using a voltmeter. Often, you can replace the faulty diode to correct the problem, or choose to change the whole alternator.

3. Loose alternator mounting bolts- these can cause the alternator to move about and lead to other problems. These only need re-tightening, and the alternator will continue to operate without any issue.

4. A jammed tensioner- sometimes, the tensioner will corrode and jam. When that happens, your best bet would be to replace it.

5. Broken or frayed wires- wires that have lost insulation can no longer work as expected. There could be shorting and improper battery charging. Replace any cables that seem worn out.

6. An undercharged battery – it means the alternator is not producing enough power. There could be several reasons for that. You may need to carry out tests to find out the cause, and then you can determine what action to take.

7. An overcharged battery- the problem could be with the regulator. Because it controls the alternator output, a faulty one may mean voltage that goes below or exceeds the normal values.

8. Battery not charging at all- check the connectors. It could also be a blown fuse. These may need to be replaced or cleaned as a means to restore the proper working of the alternator.

Alternator Rebuild

Alternator Rebuild
Source :

Apart from the temporary alternator fix measures, you may want to consider some longterm options that are also less costly. Rebuilding the alternator is one of them and a popular one. It’s often a simple process and one that anyone can do without prior knowledge of car mechanics; only some basic alternator knowledge.

Many auto parts manufacturers sell alternator rebuild kits. These are cheaper than buying a brand new unit. The kits contain all that you need to replace the various components plus instructions on how to it. If you’re considering alternator rebuild, here is the procedure.

The Steps To Alternators Rebuild

  1. Disconnect the battery terminals.
  2. Remove the drive belt.
  3. Loosen and remove the alternator mounting bolts.
  4. Slide off the alternator.
  5. Start by removing the alternators back cover. You only need to unscrew it.
  6. Check the bearings for wear. If they don’t appear to be fitting tightly or if there’s noise when you spin the pulley, you need to replace them.
  7. Loosen and remove the resistors.
  8. Remove the rectifier, together with its wire leads.
  9. Mount the new rectifier by re-inserting the screws and soldering the lead wires as appropriate.
  10. The alternator brushes are held into place by screws. Loosen them and simply lift off the old brushes. Place new ones in their place and ensure the springs behind are correctly positioned.
  11. Unscrew the regulator, remove it and install the new one.
  12. Now that you have replaced the parts that can be fixed, use a brush to clean the other components.
  13. Replace the resistor, the back cover and reconnect the electrical connection you had removed earlier. You may test the rebuilt alternator to ensure it’s functioning properly.
  14. Mount the alternator back on the engine bay and bolt it up. Return the drive belt, ensuring the correct tension.
  15. Reattach the battery cables.

This youtube video will show how to repair, rebuild the alternator and replace it’s regulator.


You can choose the option that works the best for you subsequently after all information on how to fix an alternator. If the alternator is low-mileage but experiencing problems, you may want to consider checking the source of the malfunction and fixing that.

An example is a new alternator that was installed to an old drive belt. It may show symptoms of damage when it’s the belt that is the problem. In such a case, you do not need to install a new alternator but a new belt.

When choosing whether to repair, replace, or rebuild an alternator you may want to take into account the longterm expenses. The alternator repair cost may be much less than the cost of buying a new alternator. It could still be cheaper than a rebuild.

But then, it only provides a temporary alternator fix, and very soon you may find yourself having to dig deep into your pockets. A new unit would be much better, and a rebuild much welcome if the budget doesn’t allow. You want the best for your car but also your pocket.

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