Replace your alternator

Edited by Ephraim, Charmed, Sadelape, Eng and 9 others

This article will discuss how to change your vehicle's alternator without visiting a mechanic. Going to a local shop can cost a lot of money, so here are some simple steps to assist you to do it on your own, without spending too much.

Do a quick check to see if your vehicle's alternator has a problem by turning the vehicle on, and then turning off the positive battery post. If the vehicle shuts off, then there is a problem with your vehicle's alternator. Another indication you have a problem with your alternator is if a fully charged battery is easily drained.

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  1. 1
    Unplug the electrical cords to avoid being electrocuted when changing the alternator
    Look for the positive post and unplug it from the battery. Normally it has a red coating. Leave the negative cord connected to the battery, as it is not necessary to unplug it.
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  2. 2
    Be aware, the position of the alternator is different for each vehicle
    Check online for a diagram or draft. If you have some friends or a relative that has the same car as your, you can simply ask for their help in locating the alternator.
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  3. 3
    Loosen the serpentine belt, which is stretched across a pulley system on your vehicle
    Loosening the belt before you remove the alternator. If you don't loosen the belt, you won't be able to pull off the alternator in the later steps. Use either a simple ratchet to complete this step, or a serpentine belt tool. Before loosening the belt, memorize the setup or better yet, take a picture, so when you go to replace the belt, you'll have no trouble reassembling.
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  4. 4
    Replace the bolts that you removed to take the belt apart
    Those bolts will be used to level the alternator out for removal. After you have replaced the bolts, you will be able to continue on to the next steps. You will need to replace 2 to 4 bolts.
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  5. 5
    Identify the bolts that secure the alternator
    There are some bolts that don't actually secure the alternator, and don't need removing.
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  6. 6
    Use a socket wrench to remove the bolts that secure the alternator
    As mentioned, between 2 and 4 depending on the make of the vehicle.
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  7. 7
    Once the bolts have been removed, take the alternator out of the dock
    Now you have to disconnect the electrical wires attached to the alternator. Do this carefully. If you damage anything in the process, it will be costly for you to repair. Use the tool specified, regarding size, to successfully remove the electrical wiring attached to the alternator.
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  8. 8
    Take the alternator to a car repair shop or auto parts store to get the perfect fit or same sized alternator as the one you need replaced
    Sometimes you can customize an alternator by using your old alternator to build a new one. This is a lot cheaper than buying a new alternator.
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  9. 9
    Make sure the alternator you've purchased is the correct one for your vehicle before attempting to install it
    Also make sure it will fit into the assembly of your vehicle and is compatible with the serpentine belt. If you've had your new alternator rebuilt from the old one, it will have already been inspected.
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  10. 10
    Place the new alternator where the old one was
    Make sure you have connected all the wiring before you secure it with the bolts. Make sure that you did not rip or tear the coating of those wires as it will cause a problem.
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  11. 11
    When replacing the bolts, make sure the alternator is in the correct position
    If you have trouble screwing in the bolts, don't force them. Try adjusting the alternator until the bolts are easy to screw in. This will avoid a lot of costly problems in the future.
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  12. 12
    # Re-attach the pulley used to hold the serpentine belt in place
    Adjust the bolts on the alternator and make sure that everything is in place and fits perfectly. Replace the serpentine belt before you tighten the pulley system.
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  13. 13
    Put the serpentine belt back around the pulley system
    Refer to you're the diagram you downloaded from the internet to ensure a perfect fit. When reattaching the belt, wrap it back around the pulley. Do not forget to tighten the pulley bolts to secure it in place. Once you have tightened the pulley bolts, it will run smoothly.
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  14. 14
    Reconnect the positive battery cable, in order to give the vehicle the power to start
    Reconnect the negative post as well, if it was disconnected during the process. Make sure you tighten the bolts on the battery posts correctly, not doing so can result in the battery not fully powering up the vehicle when starting it. If there are other wirings, like converters or any others that connect to your vehicle's battery, plug them all back in. These are all necessary for the successful running of your vehicle.
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  15. 15
    Start up your vehicle to see if you have connected the battery posts correctly
    This doesn't necessarily mean the alternator is working. To check if your alternator is working properly, you will need to start the car. While it's running, disconnect the positive cable from the battery. With the positive post of the battery disconnected the alternator will either keep the car running, or the car will shut. If your vehicle shuts off, either your alternator is bad, or you have connected it incorrectly. If the vehicle remains on after disconnecting the positive post, your alternator is working and you have installed it properly.
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Questions and Answers

How to fit the positive battery cable on your alternator?

Before you proceed with replacing the positive battery cable of your car's alternator, know there are two wires in your positive battery cable - a shorter one which is easier to fix and a longer wire that can be more challenging to work on.

For this procedure, you will need a 10-millimeter and 12-millimeter socket wrench. You will also need a socket extension, socket driver, a 13-millimeter box end wrench, ties for the cable, and a floor jack.

Now let us proceed to the step-by-step instructions for replacing the positive battery cable:

  • Lift the hood and disconnect the negative and positive battery terminals.
  • Displace the protective cover of the battery.
  • Take out the hold down bolt clamp located at the base of the battery's front. Remove the clamp and remove the battery from the car.
  • Remove the short wire from the fuse box. Locate it on the positive terminal and follow it to its termination point. Look for the fuse box. Remove the black cover and the nut holding the cable's end in place. Lift the end of the cable from its mounting screw.
  • Start removing the long end of the cable. It is connected from the starter solenoid to the alternator through a 12-millimeter nut. Use a 12-millimeter socket to remove the nut from the end of the cable.
  • Look for the nut mounting the cable to the starter. With a 12-millimeter socket, remove the nut and the cable from the mounting screw. Remember the two nuts differ in size, the smaller one for the starter and the larger for the alternator.
  • Cut the cable tie holding down the cable to the starter solenoid.
  • From the top of the engine, look for the three hold down clamps. From the battery connection, you will see a 10-millimeter bolt. Remove it using a 10-millimeter socket and socket extension.
  • Now, search for the second hold down clamp using a 12-millimeter nut. Look for it and remove with a 12-millimeter socket and extension. The second hold down clamp uses a 12-millimeter nut. Locate the nut and remove using a 12-millimeter socket and extension.
  • The third hold down clamp has a 10-millimeter bolt. With a 10-millimeter socket and extension, remove the bolt. While doing this, be extra care not to move the temperature sensor in your vehicle's wiring. It is very close to the where the extension socket is inserted.
  • Displace the remaining hold down cables. There are two ties that hold the short and some long cables. Let the 2 rubber guides keep the long cable in its position.
  • Slowly pull out the long cable. Once removed, inspect it to see if it's been disturbed.
  • Take out the three clamps from the old cable and connect them on the new cable. Position them in the same orientation as the original.
  • To install the new cable:
    • Simply do the reverse of the removal procedures.

The alternator does not connect through a wire to the battery. The only cables that will be connected to the battery will be the ones from the car directly from the positive or negative posts.

What to do if a bolt breaks when taking out an alternator?

If the bolt breaks, you will need to replace the bolt with a brand new bolt. Without specific tools, it will be difficult to get the broken bolt out of the alternator. You can visit an auto garage. For a reasonable fee, they can get the bolt out of your alternator. Some people are reluctant to take their car into an auto shop, but it's a small price to pay to make sure this is taken care of properly.

If you tighten the battery post and the car turns off does it mean the alternator is dead?

In order to check if your alternator is good you will need to perform the following:

1. Start your car.
2. Take off your positive post while car is running.

If the car turns off then your alternator is bad. If the car stays on then that means your alternator is good.

Does alternator have to be ordered or do they stock them somewhere?

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I just replaced alternator but when I pull battery cables off, the car shuts off still? Could something else be wrong or is it faulty replacement alternator for sure?

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Battery light is ON a Saturn 1999 sl1?

I replace spark plugs on a Saturn sl1 1999 now battery light is ON

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The bolt is spinning and won't tighten or come out, any suggestions?

Any suggestion on how to take the bolt out

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I just replaced my alternator in my 89 Toyota 4runner?

Everything was working just fine, but it threw the belt. So I loosened the alternator. Got the belt to its respective area, but in such a hurry I forgot to disconnect the negative terminal from the battery. Something on the alternator arced and now my truck won't do anything. No dash lights, nothing. I have tried: Jumping it. I think it was caused by: I left the battery connected while fiddling with the alternator. Just want to know the potential damage I may have done

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Car won't start after replacement with alternator and left battery connection on battery?

I was replacing alternator and left the positive battery connected and sparked in the ground on the alternator and now no power at all. I have tried: Checked for blown fuses, and tried jumping the cars battery. I think it was caused by: Leaving battery plugged in

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Is it really safe to leave negative battery terminal connected?

I just think it would be much safer to disconnect both terminals when working on the alternator. You can risk closing the circuit just from working with metal tools on the positive terminal post while the negative is still clamped, and this danger would extend to any other electrical connection on the vehicle (of which there are numerous, often hidden), including the alternator. In my opinion, it is never safe to disconnect the positive terminal while the negative is still connected. I've seen people get badly burned thanks to a bad combination of wedding ring/jewelry, metal tools, and accidentally brushing against a grounded metal surface in the engine bay while the negative battery clamps are still fastened.

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If you have problems with any of the steps in this article, please ask a question for more help, or post in the comments section below.


Article Info

Categories : Automotive

Recent edits by: jakecrew, dorotheastreet, Melsan

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