How Long Do Alternators Last?

The life of your alternator depends on how often you drive and how hard you drive.

In general, an alternator lasts about 100,000 miles. In terms of years, an alternator can last between 5 and 10 years if it’s in good shape and has been well cared for.

If you’ve neglected your car’s maintenance or had it serviced by someone who didn’t know what they were doing, then your alternator may not last as long.

A good rule of thumb is that if your car starts to make a noise when you turn the key, it’s probably time to replace your alternator.

How to tell if your alternator is bad?

If you suspect your alternator is bad, there are a few things you can check.

Voltage output

The first thing to do is to take the voltage output of the alternator and compare it to the voltage output of the battery. You should see a difference between these two readings, but not by much.

If there’s no difference at all, or if they’re close enough together that they could be interchanged (for example, 13 volts on both), then it’s likely that your alternator has failed and needs replacing.

Voltage output using a voltmeter

A voltmeter allows you to get very precise readings regarding how much voltage an object produces or stores up—in this case, your car battery and alternator respectively!

To measure their respective outputs using a multimeter, clamp both leads onto each respective component via its positive post (black) and negative post (red).

Make sure when doing this that nothing else connected nearby can cause interference with any current flowing through those posts—otherwise there may be inaccurate readings from either device due to interference!

Keep in mind too that most cars’ batteries will have more than one connection point where power can enter into them through extension cables; so make sure everything stays connected properly before proceeding further down this list.

How to fix a bad alternator?

The first step in replacing your alternator is to test it. This will help you determine whether the problem is with the entire unit or just a few components.

Here are some things to look out for when testing:

Voltage and electrical output:

The voltage should be between 14-17 volts. If it’s lower than this, then there’s a problem with your alternator.


A healthy alternator should have less than 20 ohms of resistance across the terminals of its internal components, including brushes, diodes and field coil.

The resistance of these parts will change depending on their age; for example, new brushes have very little resistance compared to worn ones that might have hundreds of ohms per inch.

If you’re unsure what kind of condition yours are in, consult an automotive supply store or mechanic who can tell you how much they should read based on their make and model year and mileage history

How to replace an alternator?

If you’re looking to replace an alternator, this is the guide for you. We’ll show you how to change out your alternator belt, pulley and regulator, as well as any other parts that may need replacing along the way.

To begin with, locate and remove the battery from your vehicle. Then locate and remove the negative terminal from both batteries (otherwise known as a ground).

This will ensure that no electrical sparks fly when working on your car’s electrical system, which could be fatal if there is any oil or water present on your hands or tools during this step of the process.

Next up: Locate where your old alternator was installed in relation to its mounting brackets. If possible try not to take these brackets off until later in this process because they will provide an important reference point for reinstalling new parts later on in our journey together!

Once located simply use some wire cutters or pliers to cut them off completely so they won’t be reused when installing new ones later down road ahead . . . get ready now though because once those come off things can get messy really fast here so stay focused big boy!

How to test an alternator?

Testing an alternator is a simple process. This guide explains how to test your car’s alternator and replace it if necessary.

A battery should be tested first, since it can cause problems with your alternator. If you’re experiencing starting problems, look at the battery first.

If you have a nearly dead battery, you should charge it before proceeding with testing the alternator.

How to ensure your alternators last as long as possible?

Alternators are relatively simple machines, but they can still be finicky. Following good maintenance practices can help ensure your alternator lasts as long as possible.

Clean and properly fill fluids

Use the recommended type of oil for your car’s engine, transmission and differential (if applicable). The same goes for the power steering fluid and brake fluid. Keep an eye out for leaks that might indicate a problem with one or more of these systems, which could lead to premature wear on your alternator.

Have regular maintenance performed

You don’t want just any old mechanic working on your vehicle; you want someone who knows what he’s doing! This means making sure he understands what makes up a proper service schedule for all areas of interest: brakes, belts/hoses/shocks etc…

That way any problems can be caught before they become major malfunctions requiring expensive replacements like new spark plugs or distributors caps which may not even fix anything anyway because there might be bigger issues like bad wiring somewhere else inside that needs replacing from scratch instead!


Alternators are designed to last up to 100,000 miles, but it’s possible for them to go bad before they reach that point.

A good quality alternator should last anywhere from 6 to 8 years with regular use. If you’re driving a lot or have a high-demand vehicle like a truck, you may need to replace your alternator more often.

If you notice your battery is getting drained faster than usual, one of the first things you should do is check your alternator.

Steven Hatman
Steven Hatman

We break down every information into easy-to-understand articles that cover all the categories anyone who owns a car needs to know about, such as oil , brakes , tires and etc. Our car guide is free and updated regularly for you to use as a resource, not only when you have an issue with your car but even before buying a new or used car! We also give tips on what to look for in each category or part of your vehicle.