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Thread: Alternator exciter reluctant to activate

  1. #1

    Alternator exciter reluctant to activate

    Iím having an issue where my alternator is not charging when the car is started until the motor revs over 2,000rpm. This is the second alternator and the first had the same issue although it needed to get 3,000+rpm before charging. The first alternator stopped working entirely after about 1,500 miles. Both are new Valeo alternators.

    The alternator light comes on at start up and does not go out until I blip the throttle to the previously mentioned 2,000rpm. I have confirmed this with a multi-meter as well. Iím thinking it might be the exciter circuit in the voltage regulator but what are the odds of two new alternators having the same issue?

    Any help would be appreciated.

  2. #2
    Senior Member
    Join Date
    Apr 2004
    35,000 ft
    I found this useful when tracking down similar issues.

    If you’ve got a lower wattage bulb, or (god forbid) LED indicator lamp. Or swapped to an alternator with a built in regulator, the factory recommended a resistor be placed inline with the lamp on the dashboard. 91ohm and 5 watts. Or just use a 5 or 6 watt bulb
    looking for 1972 911t motor XR584, S/N 6121622

  3. #3
    Thanks. My kingdom for a Radio Shack!

  4. #4
    Mike, sent you a PM.

  5. #5
    Senior Member
    Join Date
    Oct 2008
    Burford, ON, Canada
    Exactly what alternator bulb are you using? As mentioned, an LED bulb CANNOT be used in this application.
    Porsche Historian, contact for Kardex & CoA-type Reports
    Addicted since 1975, ESR mbr# 2200 to 2024 03
    Researching Paint codes and Engine Build numbers

  6. #6
    Thanks Rick, and Dave it's a standard bulb. I even swapped it with another in the cluster to see if there was a problem with that particular one.

  7. #7
    Thanks to Blucille and Rick the problem has finally been solved.

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