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How to Change an Alternator

When a vehicle's alternator is functioning properly, it will put out between 13 and 18 AC volts that power the electronics and ignition system while recharging the battery. But, if it delivers less than 13 volts, the alternator will fail to keep the battery recharged. You can save money when you replace your alternator by doing it yourself and following the steps below.

StepsEdit

1
Disconnect the positive battery cable. It should be red.
2
Locate the alternator on your particular vehicle.
3
Use a serpentine belt tool to loosen the belt and move it off the pulley of the alternator.
4
Put back the bolts that hold the alternator in place. It will be a minimum of 2, and no more than 4, bolts depending on your make and model.
5
Employ a socket and ratchet to loosen and remove the bolts.
6
Pull out the alternator, then unplug and remove the nut for any electrical connections.
7
Remove the alternator from the engine and take it to the parts house in order to get a new or rebuilt one.
8
Inspect the new alternator, while still at the parts house, comparing it to the old one. Make sure the voltage regulator and pulley match up to the old one. If it does not, get the parts house to put the old pulley assembly on the new one.
9
Reverse the process to install the new alternator.
10
Connect the electrical plugs and wires onto the new alternator.
11
Slide the alternator into place and begin threading the old bolts in the right position.
12
Put the alternator pulley back into place, bolting it down. Be sure to check the alignment with the belt tensioner pulley.
13
Use the serpentine belt tool to get the slack you need and slip the belt back over the alternator pulley. Now release the tool by putting tension on the belt.
14
Reconnect the positive battery cable.
15
Start up your car and make sure the alternator is charging.

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Community Q&A

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What do I do if my alternator fails?

Answered by wikiHow Contributor
- Start out by replacing it. You might also want to test your battery to see if it still has juice since the alternator, which is supposed to charge it, failed. Also buy a new wiring harness to make sure maximum power is going throughout your car.
Thanks! 4 0
What is a serpentine belt tool?

Answered by wikiHow Contributor
- It's usually a long ratchet or "breaker bar" used to loosen the bolt on the belt tensioner so that the serpentine belt becomes loose.
Thanks! 4 0
What tools are needed to change an alternator?

Answered by wikiHow Contributor
- A set of sockets or spanners, and a lever to hold pressure on it to keep the belt tight when installing the new one.
Thanks! 14 7
How can I be sure that the alternator is the problem with my car?

Answered by wikiHow Contributor
- If you aren't sure how to diagnose this problem yourself, you can take your car to the shop and have them check your alternator (even if you do the repairs yourself).
Thanks! 2 0
Will the alternator start with a jump start?

Answered by wikiHow Contributor
- Yes, they often will.
Thanks! 9 9
Do I have to leave the negative cable connected?

Answered by wikiHow Contributor
- No, it is best to remove battery cables and clean the terminals while it is off.
Thanks! 6 6
How do I change the alternator in a 1989 Cadillac El Dorado?

Answered by wikiHow Contributor
- Changing the alternator on most cars is generally the same. Find the alternator (has to be connected to the serpentine belt), and then look up steps to replace it. The main difference in cars is where the alternator is and how it's mounted.
Thanks! 3 2
My van idles a thousand miles per hour since I put in a new alternator. Why is this?

Answered by wikiHow Contributor
- You most likely knocked the timing chain off just a bit, or the alternator you put on has a higher voltage output than the original.
Thanks! 3 8
What tools do I need to change the alternator on my '03 Acura RSX?

Answered by wikiHow Contributor
- You need a long (heavy) flat-blade screwdriver, an adjustable wrench, a box or open wrench - or two, depending on the size of the nut to be loosened.
Thanks! 2 5
How do I check my voltage on my new alternator?

Answered by wikiHow Contributor
- Your battery is supposed to be at about 12 to 14 volts, if your alternator works that is where it will sit, maybe a little higher. You can plug a sensor onto the alternator and ground it off away from battery, then read it.
Thanks! 0 0

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How do I remove an alternator from a car?

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How do I clean and check my alternator?

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How can I tell if I need to change an alternator or a car battery?

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Where does the little black wire go on the back of the alternator?

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VideoEdit

TipsEdit

Take photos with your digital camera as you remove parts. This shows what came from where. It will also make it easier to remember the sequence when you put it back together.

3 Helpful? 2
If you have trouble finding the serpentine belt tensioner, use the drawing of the belt that is most likely located in the engine bay compartment.

1 Helpful? 2
Many auto parts houses will loan you the serpentine belt tool for a small refundable deposit.

3 Helpful? 4
When you return the serpentine belt tool, ask the parts house if it will check the voltage your new alternator is putting out. Most parts houses will do this for free. The voltage should be at least 13 volts.

2 Helpful? 3

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WarningsEdit

Disconnect the positive battery cable before you work on any electrical parts in your vehicle to prevent shorting out the electrical system and damaging the electronics.

2 Helpful? 1
When putting the old bolts back onto the new alternator, do not tighten them down until all have been added.

1 Helpful? 1
Always allow the engine to cool down before you begin working near it to prevent burning yourself.

0 Helpful? 4