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Summary
  • The alternator rebuilding process involves a thorough inspection of the internal and electrical components before replacing all the parts that have been damaged.
  • A rebuilt alternator generally reuses major parts like the housing, stator, and rotor. The entire component is dismantled and inspected separately.
  • A dedicated DIYer can purchase an alternator rebuild kit for anywhere between $25 and $60.

Without a functioning alternator a vehicle will only run until the battery dies. So what are your options when you have a bad alternator?

The easiest route is to buy a new or remanufactured one, but rebuilding an alternator is also on the table, and a lot of drivers go for it.

Damaged Alternator: Rebuild, Replace, or Remanufacture?

When it comes to dealing with a damaged alternator, there are generally three ways you can go about it: rebuild it, replace it, or get a remanufactured alternator.

Alternator Rebuild

A rebuilt alternator generally reuses major parts like the housing, stator, and rotor unless one of these parts is the problem, and sometimes they are. The rotor can be open, the stator windings can be shorted together, and diodes can be bad in the rectifier.

In a rebuild, the entire alternator is dismantled and inspected separately. Knowing how to inspect each component is important.

Before you even tear the alternator down, you can do a diode check using that function on a DVOM that has it. You can see how to do that in this short video:

The alternator rebuilding process involves a thorough inspection of the internal and electrical components before replacing all the parts that have been damaged.

Compared to replacing a damaged alternator, rebuilding one is also the more cost-effective route, depending on what needs replacing, and you need to have a source for replacement parts. And again, some alternators are a lot harder to disassemble and rebuild than others.

, Is an Alternator Rebuild Worth It?

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: If you get in over your head, you can always just choose to buy a new or remanufactured unit. You might even consider a used one from a salvage yard, but you never know how much life is left in one like this.

How Much Does It Cost to Rebuild an Alternator?

A dedicated DIYer can purchase an alternator rebuild kit for anywhere between $25 and $60. Most kits contain the following parts:

Alternator Replacement

Getting an alternator replacement is arguably the most hassle-free way to resolve your vehicle’s alternator problems. You won’t have to deal with the complicated process of picking an alternator apart and putting it back together.

Instead, you only have to buy a high-quality alternator replacement that matches your vehicle’s specifications and get a licensed mechanic to install it for you. You can even do the job yourself if you’re used to tinkering with your vehicle.

It can cost anywhere between $100 and $600 to replace a bad alternator.

Remanufactured Alternator

A remanufactured alternator requires factory-processed repair procedures, Similar to rebuilding an alternator, remanufacturing a damaged one also involves similar processes like replacing the voltage regulator, diodes, and brushes, among others.

Remanufacturing an alternator, however, follows strict guidelines and procedures unlike rebuilding one, which you can do from the comfort of your home.

Remanufacturing an alternator is essentially a restoration of a damaged alternator to its full functionality. You can find a restored alternator from factory-authorized remanufacturers.

, Is an Alternator Rebuild Worth It?

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Not all remanufactured alternators are created equal. It’s best to buy a new one if you have the cash rather than a remanufactured one.

Alternator Rebuilding: The Basics

If you’re attempting to rebuild an alternator for the first time, here’s an overview of what the process might involve.

Testing and Disassembly

Before picking an alternator apart, it must first be tested while it’s inside the vehicle. It can also be tested on an alternator test bench separately.

From there, the alternator can be disassembled.

More Testing

Individual components are tested upon opening the alternator. Parts that fail the specified values are replaced with new ones. These parts include the alternator windings (rotor and stator), as well as the insulating rotors.

Refinishing

During the refinishing process, the alternator is washed, sandblasted, shot-peened, and coated.

Note: When installing a rebuilt or refurbished alternator, keep in mind that the clocking position of the harness connectors can vary, depending on the clocking of the stator housing.

Simply re-clock the harness connector to face the proper angle.

Also, make sure that the rebuilt alternator has the same amperage as the old one. Get a rebuilt alternator with a higher amperage if you’ve recently installed more electronics.

Reassembly

Once the alternator has been reassembled, it will undergo another round of testing. The testing process involves placing the alternator on a test bench that applies variable loads at different running speeds.

Why Do Alternators Break Down, Anyway?

illustration showing the basic components of an alternator
This illustration shows the basic components of an alternator. | Image Source: Richard McCuistian
, Is an Alternator Rebuild Worth It?

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Some alternators are easier to disassemble than others. Some require special soldering procedures where the stator connects to the rectifier bridge, so be aware before you start.

The alternator has bearings that can wear out, but usually these are not the parts that fail on an alternator. The most commonly failing components in an alternator are the brushes. The rotor spins two slip rings that are in constant, spring-loaded contact with the brushes, and while they usually last the life of the vehicle, they do wear out eventually, and they typically wear out the slip rings as well.

The next most common failure would be a tie between the rectifier bridge and the stator–that’s the outside windings where the current is created as the magnetic field in the rotor passes through the stator core and its three windings.

Some alternators have an internal voltage regulator that includes the brushes. Chrysler alternators don’t typically have internal regulators, rather, the engine control module monitors battery voltage and controls field current, which is the strength of the magnetic field created by the spinning rotor. The regulator can fail, too.

, Is an Alternator Rebuild Worth It?

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Before you go after the alternator, make sure you know the wiring isn’t an issue. The wire that leads front the battery light on the cluster to the alternator can be shorted or cut and it will prevent the alternator from even initializing.

Symptoms of a Failing Alternator

The alternator won’t fail without reason. There are a bunch of underlying issues that could cause its failure, which is why it’s important to familiarize yourself with the common symptoms that indicate a bad alternator.

Illuminated Battery Warning Light

A common misconception about an illuminated battery warning light is that it’s immediately a battery issue.

However, keep in mind that the alternator is responsible for charging the battery and supplying voltage to various electrical components. So a failing alternator could be the reason why this warning light pops up on the dash.

A failing alternator could have a lower voltage than the normal operating range, which is typically between 13 and 14.5 volts.

A bad alternator can also cause the battery warning light to flicker.

Dead Battery

If you have a new battery that suddenly ran out of juice, you could be looking at an alternator problem, specifically a malfunctioning rectifier diode.

A faulty rectifier diode can cause an electric current to flow both ways instead of one, causing the alternator to drain the battery.

Ignition Problems

Your vehicle could exhibit ignition problems because of a bad alternator. This is because the alternator isn’t charging the battery enough to kickstart the electrical system.

If you have a bad alternator, the engine might not turn over and all you’ll hear is a clicking sound.

A failing alternator can also cause your vehicle to stall. This activity is often accompanied by an illuminated battery warning light, which signifies that the control modules aren’t getting enough power to keep the engine running.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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