Edmunds Answers



  • zaken1 04/05/11 2:00 pm PST

    The replacement alternator you installed is apparently not charging. It may be defective. This is a common problem in rebuilt alternators sold by discount parts stores. And from repeated experiences of this type; I have learned that the only place I can trust to buy a rebuilt alternator is a NAPA parts store.

    Alternatively; the alternator may be good; but the field winding may not be receiving power from the ignition switch. The alternator is protected by a fusible link; to prevent massive damage to the vehicle wiring when the alternator shorts out. Check the plug or other wires that connect to the alternator for switched voltage; which will only be there when the key is turned on. If there is no voltage in the field wires to the alternator; then the fusible link is either blown, or there are more burned wires somewhere between the ignition switch and the alternator.

    You'll need to consult a service manual or a dealership to find the location of the fusible links.

    The most common cause of internally shorted alternators is someone reversing the position of jumper cables or battery charger cables. Reversing the cable positions can instantly destroy alternator diodes. Another common error that destroys alternators is disconnecting a battery cable while the motor is running. People who do that to "test" the alternator are often destroying a good alternator.


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