What is the voltage my alternator should put out when the car is running? 348 | FerrariChat
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What is the voltage my alternator should put out when the car is running? 348

Discussion in '348/355' started by Paresh, Jul 23, 2010.

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  1. Paresh

    Paresh Karting

    Oct 5, 2009
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    Paresh
    #1 Paresh, Jul 23, 2010
    What is the voltage my alternator should put out when the car is running? 348
    Car is at 12.4 when stopped. 13.4 when running. Battery light is on. It has died only once. Belt tension is fine.

    Thanks!!!!! Also, when and if I have to build the alternator, what parts are most important to replace?
     
  2. jm3

    jm3 F1 Rookie

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    #2 jm3, Jul 23, 2010
    That sounds pretty good actually.

    JM
     
  3. BigTex

    BigTex Seven Time F1 World Champ
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    #3 BigTex, Jul 23, 2010
    13.2 - 13.4v is a good output, IMO....check the cables or the battery itself for probems..
     
  4. JoshECS

    JoshECS Formula Junior
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    #4 JoshECS, Jul 23, 2010
    Last edited: Jul 23, 2010
    14.0v is considered to be the minimum allowed output while running. Most cars are between 14-14.5v when everything is working correctly and there isn't resistance in the cables. Check to see if the voltage increases with rpm, and Ohm test the two primary ground cables. There shouldn't be more than .1 ohm of resistance.
     
  5. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #5 Rifledriver, Jul 23, 2010
    Checking voltage without load doesn't tell you much. It needs to be loaded to its rated amperage to determine condition or you will have battery problems and issues with digital electronics.
     
  6. roadracer311

    roadracer311 Formula 3

    May 6, 2009
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    #6 roadracer311, Jul 23, 2010
    My F355 puts out 14.5V at idle. My test was done with a fully charged, nearly new battery, and about 500 miles on the alternator (and whole car).
     
  7. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    9,727
    #7 Mitch Alsup, Jul 24, 2010
    With a fully charged battery, and the car running for more than 10 minutes, you should see 14.0-14.2 V. After you stop the car, this will drift downward over 8 hours to about 13.5V and after a week to about 12.8V (no discharge).
     
  8. BOKE

    BOKE Beaks' Gun Rabbi
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    #8 BOKE, Jul 24, 2010
    http://www.saveabattery.com/

    The battery maintainer is a great trickle charger that can test your electrical system under load.

    Just checking what the alternator puts out or your battery voltage without a load isn't that good diagnostically.

    I have no affiliation with the company other than buying six units from them. Amazon sells them too.

    Always check your cables too.

    Good luck!
     
  9. Paresh

    Paresh Karting

    Oct 5, 2009
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    Paresh
    #9 Paresh, Jul 26, 2010
    Thank you Brotherhood! The alternator rebuild resolved the issue. It was a Nippondenso. 100 dollars to rebuild. 1 hr to remove/install. New battery in car.

    All is good again!
     
  10. Rifledriver

    Rifledriver Three Time F1 World Champ

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    #10 Rifledriver, Jul 27, 2010


    Great guy and great product. He lives nearby and stops by from time to time.
     

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