How to Rebuild an Alternator

Co-authored by Ed Beery

Last Updated: December 9, 2022 References

Rebuilding an alternator is a fairly simple procedure, which anyone with basic automotive knowledge can accomplish. Although the construction of some brands will vary slightly, the basic anatomy of an alternator consists of the same components.^{[1]
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Research source} Follow these steps as you learn how to rebuild an alternator.

Steps

1
Disconnect the battery leads.^{[2]
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2
Remove the air cleaner for easier to access the alternator.

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3
Mark the placement of the electrical leads before removing them.
4
Disconnect the electrical leads.^{[3]
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5
Remove the vehicle's serpentine belt.^{[4]
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6
Remove the mounting bolts and familiarize yourself with their placement.
7
Pull the alternator out.
8
Remove the plastic cover from the back of the unit by unscrewing it.
9
Inspect the bearing. If it does not seem snug, or makes noise when it spins, it will have to be replaced.
10
Replace the bearing, if necessary, before moving on.
11
Undo the screw which holds the resistors in place.
12
Pay careful attention to the placement of each wire before disconnecting any.
13
Replace the rectifier by prying out the soldered leads and then undo the mounting screws.
14
Pull the rectifier out.
15
Install the new rectifier by replacing the mounting screws. Solder the lead wires to reconnect them.
16
Reinstall the screw which separates the rectifier from the brush assembly.
17
Replace the brushes by first undoing the screws which hold each brush assembly in place. Remove the brushes from their channels.
18
Clean the area of the armature shaft that the brushes contact.
19
Assure that the spring for each new brush is directly at the back, pushing into the brush slot. Install the replacement brushes.
20
Remove the voltage regulator by first removing the screw from the bottom brush assembly. Remove the screw that holds the lead into the grounding screw.
21
Install the replacement voltage regulator by replacing the screws mentioned in the previous step.
22
Use an ohmmeter or a multimeter to assure that the diodes are receiving the proper current.^{[5]
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23
Replace the plastic cover as well as both of the resistors.
24
Put the alternator back in the vehicle.
25
Reconnect the electrical leads assuring that you're installing them properly.
26
Replace the serpentine belt.^{[6]
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- When the belt is properly seated in the various pulleys, slowly adjust the tension of the belt release the ratchet, allowing the tensioner to once again place tension on the bel
27
Reinstall the air cleaner and verify that the belt tension and mounting bolts are right.
28
Inspect the heat shield at the back of the alternator to verify that it is properly installed.
29
Reinstall the battery leads.

Community Q&A

Question

Where do I buy the alternator kit for a 1997 BMW?

Community Answer

If you know how to rebuild it, look for the rebuild kit in your local auto parts store or go on car-parts.com. You can buy a used one with warranty for less than what you would pay for a new one or a remanufactured one.
Question

How do I fix the alternator of a 2004 Honda CRV?

Community Answer

You're better off replacing your alternator instead of fixing it.
Question

What if it is not charging the battery?

Community Answer

Remove one of the battery terminals, if the car turns off, most likely it's the alternator. If you can drive it, go to the mechanic or auto parts store, they will most likely check it for free. The meter should read 14 amps while it's running, don't let them sell you an alternator and find out later it was the battery.