How Much To Replace Alternator? Alternator Replacement Cost

If your car’s alternator is not functioning properly, you may be stranded on the side of the road. If this happens, you’ll surely need to find a mechanic that knows what they’re doing, which can be difficult if they don’t have any experience with car alternators. The good news is that this guide will provide you with everything you need to know to fix your car’s alternator issues.

To start, let’s take a closer look at what an alternator is and why it malfunctions. Then, we’ll move on to various ways in which you can diagnose the issue and follow through with repairs. Finally, we’ll explore different types of alternators and how to replace them if needed.

What is an alternator?

An alternator is a small device that converts alternating current (AC) from the battery into direct current (DC). It’s located near the engine and converts mechanical energy in the rotating components to electrical energy.

The key function of an alternator is to charge your car’s battery and provide this stored power for starting the engine. To learn more about how an alternator works, check out this infographic.

If you want to understand what is going on with your car’s alternator, it’s important that you know how it functions. If you’re unsure how your car’s alternator operates, this guide offers a great overview of what you’ll need to know before beginning repairs.

Why does an alternator malfunction?

An alternator is a device that converts mechanical energy into electrical energy. It’s used to regulate the alternating current (AC) coming from your vehicle’s battery, which then powers your car’s electrical system and components like the headlights, radio, side view mirrors, etc.

Car wiring repair.

The most common reasons for an alternator to malfunction are loose wires or terminals as well as a failed regulator. If you notice anything unusual with your car’s behavior, it may be time to replace your worn-out alternator.

Fixing Alternator Issues

An alternator is an essential part of your car’s electrical wire system. It converts the electricity from your battery into mechanical energy, which powers your car’s accessories. When the alternator isn’t working properly, it can cause a number of issues with your car’s system.

You might notice that your headlights won’t turn on or that the air conditioner doesn’t work anymore. Additionally, if the alternator is not working properly, you may experience lower fuel efficiency and a decreased lifespan for your car.

Low fuel car dashboard.

If you suspect there is a problem with your alternator, it’s important to take it in for inspection as soon as possible. If not taken care of right away, you could end up stranded on the side of the road without any electrical power!

Different Types of Alternators

There are three types of alternators: the conventional, the modified, and the dynamo.


The conventional alternator has a stationary field that rotates with the engine. This type of alternator does not produce power surge as well as other types and poses some maintenance issues such as leaking oil. However, it is affordable, compact, and easy to maintain. For motorcycles and cars made prior to 1975, this is the ideal type of alternator.

Automotive conventional alternator.


The modified alternator is similar to the conventional one but has an electric generator that provides electricity for accessories like turn signals or radios. It also offers higher power surges than other types of alternators.

Electric alternator inside a car’s engine.


Finally, there is a dynamo that makes use of a rotating magnet as its base and produces electricity from kinetic energy through friction in metal surfaces on a constantly moving rotor that spins at high speed.

This type of alternator can generate power surges more rapidly than conventional ones which make it more suitable for charging batteries at higher speeds and producing electricity at lower speeds with less voltage drop.

A dynamo alternator laid out on a table.
💡 However, it's important to note that some vehicles are only compatible with certain types of alternators due to size or functionality differences.

How an alternator works

An alternator is a type of electric motor. It’s designed to generate current in both directions. This can be confusing, as the term “alternator” doesn’t just refer to one machine but two different machines.

One of those machines is called a dynamo and the other is called a generator. The dynamo’s job is to convert mechanical energy from the engine into electrical energy that runs through the charging system and back into your battery to power your vehicle.

The generator turns over the engine’s internal combustion engine (ICE) and produces electricity for use by charge controllers, instrumentation, electrical loads, etc.

Diagnose your problem

When diagnosing your alternator, you need to know the operation of the car first. If it’s not running correctly, you can test out different charging systems and equipment to determine exactly where the problem lies.

A qualified mechanic will also be able to diagnose your problem for you by checking voltage levels and adjusting internal components as needed. And once diagnosed, they’ll prioritize a repair or replacement over anything else.

This is just one step in the process of diagnosing an alternator problem; there are many more steps involved in this process. You can find out more information about diagnosing an alternator issue on your car’s service manual.

Testing the charging system

Testing the charging system will involve checking voltage, current, charge rate, and alternator shaft rotation.

To start, check the voltage with a voltmeter. If there is no voltage present at the alternator output terminals, then the alternator is likely defective. Once you have determined that the alternator is not working, you will need to test for charging system faults.

In order to do this, first, connect a multimeter across the battery positive and ground terminals. The meter should show continuity when the engine is running and pulsing with a steady 12V when the engine stops or tapers off.

Auto mechanic checking the fuse in a car using a digital multimeter.

If your meter shows no continuity in any of these cases, then you may have a faulty wiring harness or faulty alternator output terminal connections. To troubleshoot this issue further, disconnect both of these wires from each other and reconnect them.

If you get continuity on all three leads of your meter now and still don’t see charging system fault codes on your diagnostic trouble code (DTC) list after driving for 20 minutes at idle speed, then it’s likely something else is wrong.

Maintaining and repairing your alternator

To maintain your alternator, you need to make sure that it’s receiving regular oil changes. This will help keep the bearings and internal parts of your alternator in good shape.

Another important task for your alternator is allowing for sufficient cooling. If you neglect this step, the air temperature can cause problems with the internal operation of your alternator.

If you have a problem with your charging system, you should replace it as soon as possible. The old one can cause problems down the road if left unattended. The best way to diagnose an alternator issue is by taking your car to a professional mechanic or by using a diagnostic tool like CarMD Auto Repair Diagnostic Toolkit (code name: “NCAA”).

A carMD Pro Scan software and service tools.

Checking battery voltage

Before you diagnose your alternator or alternators, it’s important to check the battery voltage. This step can help pinpoint any problems with the charging system.

If the battery is not adequately charged or has been drained by a faulty alternator or alternators, it can cause problems like starting and running issues. If this is the case, you’ll need to replace your battery.

Mechanic checking voltage level of car battery.

If you’re not certain what is causing the problems, checking voltage can help determine if something is wrong with the wiring or charging system.

Inspecting electrical connections

It’s important to start with an inspection of the electrical connections. With the engine turned off it’s a good idea to visually inspect the alternator and its connections.

Look for signs of corrosion, leaks, broken wires, or faulty wiring. If you see any issue, don’t delay in replacing the alternator. It’s always better to replace it now than wait until something goes wrong and you’re forced to replace your engine.

Replacing Alternators if Needed

If you’re having issues with your car’s alternator, it can be a little tricky to diagnose the problem. That’s because the symptoms can vary based on what type of alternator your vehicle has. However, if you’re still unsure about what’s going on, it may be time for you to replace your alternator.

The good news is that there are several ways in which you can tell whether or not your car needs a new alternator. One way is by checking its voltage output. If the voltage output is low, then it may be a sign that the alternator needs replacing.

A car battery out of the engine.

Another way is by listening for unusual noises coming from the engine compartment during driving or when your car is idling at a stoplight. Here are some other signs that let you know when it might be time to replace an alternator:

–      Your battery drains faster than usual

–      Your battery runs out of power before reaching 60 mph

–      The car begins shifting roughly while driving

–      The engine shakes while idling


An alternator is an essential part of your car’s electrical wire system. It converts the electricity from your battery into mechanical energy, which powers your car’s electrical system.

The most common reasons for an alternator to malfunction are loose wires or terminals as well as a failed regulator. If you suspect there is a problem with your alternator, it’s important to take it in for inspection as soon as possible. There are three types of alternators: conventional, the modified, the stationary, and the modified.

Avatar photo
About Brock Rangel

Hi, I am Brock, and I am the lead editor/photographer for TheCarColony. I have been a mechanic for over 14 years now, and I am here to spread my car knowledge across the web!

Leave a Comment