How to disassemble an alternator

Written by david eiranova
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How to disassemble an alternator
The electricity that powers headlights like these is supplied by an alternator. (Shiny car with silver paint. Water drops on the hood. Car lamp. image by Christopher Meder from

When automotive technicians discover that there's a problem with the alternator, they often recommend buying a new replacement alternator or having the existing one rebuilt (which basically involves putting a whole new set of innards in the existing housing). But if you have the time and the inclination, simply disassembling the alternator might reveal a cheaper fix, like replacing worn out brushes, if that's all it needs. What follows is the recommended method to disassemble your alternator.

Skill level:

Things you need

  • Crescent wrench
  • Allen wrench (if needed to hold the shaft)
  • Socket wrench
  • Bearing puller
  • Plastic or glass hammer
  • Small wrench (to open the diode pack if necessary)

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    Disassembling an alternator

  1. 1

    Disconnect the battery. The car's sensitive computers could be damaged if there is a short while you are disassembling the alternator.

  2. 2

    Remove the alternator from the vehicle. To do this, loosen the belt and slide it off the pulley. Then remove the bolts that fasten the alternator to the front of the engine, disconnect the wires that run into the alternator and take the alternator off, making sure to note the location of the wires that were connected to the alternator. Consult a shop manual for detailed instructions on disassembling the alternator--the next steps in this article, although comprehensive, may not be suitable for your alternator.

  3. 3

    Put the alternator in a vice, and using the crescent wrench and the Allen wrench (if needed to hold the shaft) remove the pulley nut, which is located at the centre of the pulley next to the fan.

  4. 4

    Using a bearing puller, remove the pulley and then remove the through bolts that run from the drive end frame (where the pulley is) to the diode end frame. Tap the drive end frame lightly with a brass or plastic hammer. Remove the drive end frame.

  5. 5

    Remove the rotor, stator, diode pack, brushes and assorted bearings, O-rings, bushings and hardware from the alternator. Place these items on a work table so as to have a better idea of where they go when you reassemble the alternator.

Tips and warnings

  • Not all alternator repairs need to be completely disassembled. For example, to replace worn alternator bearings there is no need to remove the diodes.
  • If you get grease or oil on the brushes, do not reinstall them -- use new ones.
  • Avoid putting electrical parts like the rotor, stator, diode pack or regulator in solvent. This might ruin these parts.

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