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Alternator Replacement Cost

By Joe Ballard
Published on August 29th, 2024

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Every vehicle (including EVs) with a lead-acid battery utilizes an alternator to supply power to all the vehicle's electrical components and recharge the battery while the engine is running. This is contrary to what most people believe, which is that the battery supplies power while the engine is running. Whenever you turn on your headlights, radio, GPS, air conditioner, heater, defroster, or any other device in your vehicle, the alternator converts mechanical energy into electrical energy to power these devices. Needless to say, when the alternator fails, your vehicle will not function.

In this article, I will explain how the alternator works, the warning signs of a bad one, what causes it to go bad, and the typical cost of replacing this mini power plant.

How does it work?

It is surprising how much power today's vehicles consume. Not only is lots of power required for many devices such as power windows, door locks, heated seats, etc., but there are also sensors and modules located all around the vehicle to monitor safety systems, ABS, speed sensors, engine performance, etc., that need a constant supply of electrical power to operate.

To create and maintain this tremendous power requirement, the alternator takes power from the battery and amplifies it to deliver power to all the vehicle components while the engine is running. It also generates additional energy to keep the battery optimally charged. The alternator's magnetic rotor and copper windings create alternating current (AC), which is converted by a set of diodes in the rectifier to direct current (DC) that all devices use to operate. The DC voltage is regulated to prevent damage from overcharging or delivering too little power. Typically, the alternator will produce between 13.5 and 14.5 volts for optimal operation. If the voltage is not in this range, this could indicate that the alternator is failing or that other issues are preventing the alternator from maintaining this voltage level.

What are the warning signs of a bad alternator?

Some of the issues that may indicate that the alternator is going bad or has already failed are as follows:

A dead battery is a very obvious indication that either the battery has failed or is not being recharged by the alternator. If you are confident that the battery is good or that it tests good, you will need to check the alternator to determine if it is putting out the correct voltage. The easiest way for a DIYer to do this is to connect an OBD scanner and run the battery/alternator test. Using my Mazda Miata as an example, I connected my Innova 5610 scanner to run the Battery/Alternator Monitor test. The battery tested bad so I decided to test the alternator. The alternator test showed that the output was above the normal recharging range and recommended that I check other components in the charging system. The next step is to check the voltage regulator.

An illuminated battery warning light indicates a problem with the charging system. It could indicate an overcharging or undercharging condition usually caused by the alternator, although the voltage regulator could also cause this problem.
A pungent burning rubber smell coming from the engine compartment could indicate that the alternator is not spinning freely, causing the fan belt to burn on the pulley. This will usually be accompanied by squealing sounds as well.
If you notice that the interior or exterior lights (including the headlights) are dimmer, abnormally bright, or flickering, this may indicate inconsistent voltage from the alternator. However, it could also be a voltage regulator issue.
If you observe any unusual or odd things happening with the vehicle's devices, such as the windows going up and down slowly, the radio making crackling sounds, or the fan speed being slow, any of these issues could be associated with an alternator issue.

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Key Takeaways

It is frustrating to have an alternator malfunction because it always seems to happen at the most inopportune time. Just as with a battery, sometimes there is little warning that the alternator will fail. The best that you can do is try to understand what will typically cause an alternator to fail, such as:

Long-term wear and tear due to the age of the vehicle
Observing fluid leaking on the alternator
Noticing worn-out bearings
Hearing noise from a slipping fan belt
Incorrectly connecting jumper cables

Understanding the causes and watching for any signs that the alternator may be failing should help you identify an issue with your alternator before it fails. If you do need to replace the alternator, here are a few things that you should know if you are going to tackle this job yourself:

Most alternators can be purchased from a parts store for a lot less than the original equipment manufacturer (OEM) replacement that must be purchased from a dealership. That said, you need to be careful when purchasing an alternator from a parts store because it could be lower quality. You should always try to buy from a known good parts manufacturer.
Alternators are either remanufactured or new, but most aftermarket alternators are remanufactured, which means the core was rebuilt. Fewer cores are being returned for rebuilding on rarer vehicles so that these alternators will cost more.
The average time to replace an alternator is two to three hours. If it is easy to access, the job will be straightforward and easily handled by a proficient DIYer. Doing it yourself will save about $120 to $200 in labor costs.
The actual alternator cost can average anywhere from $100 to $350, depending on the make and model of the vehicle. Most vehicles will fall into the $350 price point due to the high energy needs that most vehicles require and if no other components need to be replaced. A rule of thumb is always to check the voltage regulator and ensure that the fan or serpentine belts are replaced as they wear out over time. If you choose an OEM replacement alternator, you should add about $300 to the whole job cost.

Conclusion

The alternator serves many important functions and is a critical vehicle component. Understanding some of the typical things that will cause an alternator to fail and heeding any warning signs will enable you to check your alternator before it goes bad. If you need to replace the alternator, you now have a pretty good idea of the costs whether you decide to DIY the job or bring it to a professional.