What Tools Do I Need to Change an Alternator?

Major car or truck repairs can be a hassle, and in the shop, they can cost hundreds, if not thousands of dollars. Doing the work yourself over the weekend can save you lots in labor costs, but this will require you having the necessary tools. Some jobs will require specialty tools to remove, replace or measure while doing the job but others can be pretty straight forward, requiring basic tools that most already have in their garage.

Changing an alternator in your car or truck is a fairly simple job, but you’ll need to make sure you have hand tools including a ratchet with a set of metric or standard sockets and a set of wrenches. Most alternators will be able to be changed out with these simple tools. If your alternator is mounted at the bottom of the engine, you may also need a jack and jack stands to raise the car so you can access the alternator from under the car.

The requirements may vary from car to car, but at minimum, you’ll need these tools to be able to access, remove, and replace an alternator. The rest of this article will walk you through how to use each of these tools to change out your alternator.

Replacing An Alternator


Before you get started, make sure that you have all of your tools and a new alternator on hand. Ensure that you have the right model of alternator and drive belt to install in your car or truck. Next, you’ll need to disconnect the battery to avoid shorting out your car.

Before you disconnect the negative cable, consult your vehicle repair manual to see if a maintainer should be used to avoid reprogramming problems from cropping up. Of course, the ignition should be in the OFF position as well.

The negative battery is denoted with a minus sign (-). Disconnect the negative battery and cover it up to avoid accidentally making contact with it during the replacement.

While you’re at it, clean the battery and inspect it for any damages. A bad battery can shorten the lifespan of your replacement battery. You can also test the battery yourself or take it in to your mechanic. Many of them will test your battery for free.

Locate and Inspect the Alternator

The alternator is mounted onto the engine, either on the front or the side, depending on the make and model of the vehicle. You might need to access the alternator from underneath the vehicle, so you’ll need a hydraulic jack, a set of jack stands to raise the vehicle.

Always make sure you jack the car properly and have all necessary safety precautions in place while working on your car.

While you’re down there, inspect the following components for damages.

  • Drive belt and tensioner
  • Battery terminal B+ voltage wire
  • Pigtail connector and harness
  • Alternator

Drive Belt

The drive belt should be changed out every 90,000 miles or so. If you notice cracks, breaks, or any other kind of wear and tear on your belt, it might be worth replacing it at the same time you’re changing out the alternator.

Examine the tensioner if applicable as well. It should run smoothly and not catch as you move it back and forth. Ensure the belt pully (idler) is aligned properly and still in good condition.

Uneven belt wear, a failing drive belt, or misaligned accessories can shorten the lifespan of the alternator.

Battery Terminal

The alternator battery wire can wear out with lots of use, so if it looked burned out or if the terminal end is melted or is missing proper insulation, the wire should be replaced immediately. Not doing so will result in reduced performance at best and an electrical fire at worst.

Pigtail Connector

The alternator pigtail and harness should be clean and intact. Loose connectors can cause a variety of problems with charging and the electrical components. Replace damaged components and use dielectric grease during installation.


It may seem pointless to check the condition of the alternator if you’re going to replace it, but contamination on the alternator can indicate problems with other areas of your vehicle that should be addressed before the new alternator goes in.

Failure to do so may shorten the lifespan of the new alternator and potentially void the warranty issued by the manufacturer. Be on the lookout for an overabundance of oil, antifreeze, or grease. A little is ok and perfectly normal, but if the alternator is soaked in any fluid type, you’ll want to shelve the repair project and find the source first.

Remove the Alternator

Working on the car

Disconnect anything interfering with your access to the alternator and unbolt it and remove it from the engine and mounting brackets using your ratchet and socket sets. Take note of where all of the connectors are as you remove the alternator. Once it’s removed, compare it carefully with the new alternator and make sure everything matches up perfectly.

If in doubt, check the installation paperwork for the replacement to make sure you have the correct unit.

Install the Alternator

Align the new alternator mounting holes and loosely fit the bolts and nuts. For some vehicles, electrical connections will need to be put in place first before you can nip up the bolts and nuts. Tighten them evenly and securely. Put the drive belt in position and move the tensioner so that the belt can be installed properly but be sure not to manipulate the belt forcefully.

This can be finnicky, so it might be wise to refer to your car manual’s repair guide.

Tidying Up

Once everything has been properly reinstalled, follow any relevant steps for the batter maintainer if you needed to use it and install new felt washers on the battery posts.

Attach the battery cable ends back to the battery, ensuring that you do the positive first and the negative last. A film of battery post grease can help prevent a buildup of acid and corrosion, prolonging the life of your battery and alternator.

Test the new alternator either with a multimeter or at your local mechanic shop. Once the car is level and everything is cleared away, test the car and keep an eye out for any malfunctions. If all is as it should be, your alternator is good to go!

Final Thoughts

Replacing an alternator can be done from home, and if you’re already familiar with doing DIY car repairs in your garage, then you’ll likely have everything on hand that you need to replace the alternator.


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