Generally in the United States, alternators are not repaired but simply replaced by rebuilt alternators. The cores are then sent to be rebuilt - and they are then resold. You will find in other countries (such as Mexico), the alternator will be pulled from the car, sent to be rebuilt and then reinstalled back in the same vehicle! This causes a much longer down time.
Home mechanics or shade tree mechanics are pretty safe tackling this repair on their own. Alternators, even when upgrading, do not have parts requiring a higher level of technologically advanced equipment.
To replace an alternator, you really only need a good set of instructions (generally accompanying the part) and a socket wrench. The cost of a rebuilt alternator runs from as little as $40 for an American made model to as much as $90 - $110 for a foreign made model vehicle. There will also e a refundable core charge on rebuilt alternators. You will get this money back when you return the alternator that you will e pulling out of your vehicle.
Before you decide that you need to replace the alternator, there are several troubleshooting items you will want to consider.
Check for blown fuses to ensure energy is getting to the battery to recharge it.
Check the battery to make sure it is functioning properly, including the wires running to and from the battery posts.
Check the belt around the alternator to make sure it isn’t too loose or too tight causing the alternator to function improperly.
Check to make sure the wires between the battery and alternator are properly matched. Even factory-installed cables can be mismatched.
If you are considering upgrading your alternator to a higher output alternator, it is important to also upgrade the wire between the alternator and the battery allowing for a higher/larger transfer of energy between the source (the alternator) and the storage unit the battery.
The alternator’s capability to send the newly created energy to the battery is directly related to the size of the wires between the two units. Using a wire that is too small for the output of the larger alternator can cause a back up of energy, heating of the alternator and eventually a failure of the alternator.
When upgrading the alternator another upgrade that must be done as well is the ground wire. An insufficient ground wire can cause as much damage to the alternator as insufficient wiring between the alternator and the battery. One tip that can save time and energy is to piggyback the wiring instead of removing the old wiring and installing new.
Energy or power follows the path of least resistance so it will accept the second wire and treat both wires as if they were one. The second wire should be fused near the alternator and battery but doesn’t need to be continuously fused to function properly.