348 alternator light at high rpms? | FerrariChat
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348 alternator light at high rpms?

Discussion in '348/355' started by TomPDX, Aug 28, 2008.

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  1. TomPDX

    TomPDX Formula Junior

    Mar 28, 2008
    558
    Oregon
    Full Name:
    Tom
    #1 TomPDX, Aug 28, 2008
    After I got my '91 TS back from its major service, I noticed that the alternator light came on at high RPMs (just for a second at 6k or higher). Then, the other day, when I got on her pretty hard, the alternator light came on and stayed on, at any RPM other than 1000 idle. My thread search suggested 2 possibilities: belt adjustment, and loose grounding wire. Anything else I should check this weekend? Is there some connection with the major service? Thanks!
     
  2. tng2000

    tng2000 Rookie

    Jan 22, 2007
    29
    Markham, Ontario
    Full Name:
    Stan B.
    #2 tng2000, Aug 28, 2008
    After you have confirmed your belt and ground, check your battery voltage with the engine off, the voltage during starting and the voltage during running at various rpms. You could have a bad battery, bad regulator or combination of both. at a full charge your voltage should be around 12.6 to 13v with no load engine off. While charging it should be around 14v. The numbers I use are general and I would suggest you check your service manual.
     
  3. ernie

    ernie Two Time F1 World Champ
    Lifetime Rossa Owner

    Nov 19, 2001
    22,613
    The Brickyard
    Full Name:
    The Bad Guy
    #3 ernie, Aug 29, 2008
    Last edited: Aug 29, 2008
    If your battery is located in the rear, check the stupidass bullet connectors. You will find one for the positive running under the airbox, and the other for the negative is located just above the battery, along the bar where the rear lower part of the splash guard gets bolted down. You'll see the bullet connectors held in place by a clip. Those STUPID things have caused more problems. They have a tendency to get loose and as a result of the bad contact the battery doesn't get the proper voltage from the alternator, or doesn't make the proper ground. I just got rid of the damn things altogether and ran solid cables for both the +/-. So check those out after you run a load test on your battery.
     
  4. TomPDX

    TomPDX Formula Junior

    Mar 28, 2008
    558
    Oregon
    Full Name:
    Tom
    #4 TomPDX, Sep 2, 2008
    Well, I checked the battery first, and it was cold dead - zero volts. That actually explains a few things/recent happenings. So I will replace that first and hope it's the cure. I will also check the bullet connectors. Thanks fellas.
     
  5. f355spider

    f355spider F1 World Champ
    Owner Rossa Subscribed

    May 29, 2001
    18,039
    USA
    #5 f355spider, Sep 3, 2008
    Tom,
    Most autoparts chain stores will perform an electrical check for free. They only need access to the battery or jump start points in order to connect up. Very non invasive and fast test. Do it after the battery replacement. It will confirm that your alternator is okay, before you kill another battery, in case it is not up to snuff. ;)
     

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