308 alternator test results

Discussion in 'Technical Q&A' started by samtheclip, Jun 18, 2004.

  1. samtheclip

    samtheclip Karting

    May 30, 2004
    Buffalo, NY
    Full Name:
    Sam Pasceri
    I just took my 81 308 GTSi to the local store to have the alternator tested. It came back with a very high volt test. The results were VOLTAGE 17.45 and MAX. AMPS 199. Here I thought my car was being under powered. They told me that the high voltage could damage the battery and other things. They actually have the bosch replacement for $70 rated 65amps. Any info on what I should do? I plan on upgrading the stereo and some other stuff and wanted a 100amp alt. YES, I know I have have this one rebuilt to 85amps. Why is the voltage to high?

  2. enjoythemusic

    enjoythemusic F1 World Champ

    Apr 20, 2002
    Full Name:
    Perhaps the voltage regulator needs replacing? As you know voltage is different than amperage so boosting amperage is ok, but make sure the voltage is proper or battery can go BOOM or catch fire.

    Ferrari UK can tell you about the downfalls of a battery exploding and catching fire :(
  3. samtheclip

    samtheclip Karting

    May 30, 2004
    Buffalo, NY
    Full Name:
    Sam Pasceri
    Where is the voltage regulator (cost)? Someone told me I had a bad diode in the alternator, could this be true?

  4. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    Your alt. is full fielding. Bad. This can cause the battery to explode. Your voltage reg. and brush pack is on the back of the alt. It usually has 2 small screws/bolts that hold it to the back of the alt. VGs are around $30-$55 new. You should replace it and that will fix your problem.
  5. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    Groton, MA
    Full Name:
    Verell Boaen
    The voltage regulator mounts on the back side of the alternator. In the 3x8 Bosch alternators, the voltage regulator has the brushes for the rotor slip rings built into it. BOSCH replacement regulators were $65 3-4 years ago.
    3rd party regulators, diode ass'ys, & slip rings are also available to commercial alternator rebuilders.

    The 308s use a non-std voltage regulator because of the voltage drop in the long cable between the alt. & the battery. Thus the regulator probably will have to be ordered.

    Usually a bad diode will drop the total Amps an alternator can put out. Depending on the way the diode bank is assembled, it's often possible for a rebuilder to press out a bad diode & replace it. Lately, mfgs have been making non-repairable diode ass'ys, but suspect the 3x8 alts are old enough so that they're repairable.
  6. fastaone

    fastaone Karting

    Jan 9, 2004
    Long Island
    Full Name:
    Peter F
    Yeah my battery went..... BANG!!! The voltage regulator went bad
    Replaced it and now is working fine under $100.00
    Buy 1 of those voltage meters that you plug in the cigarette lighter, I did because hearing that LAUD BANG at 80 mph scared the pants out me Another warning sign is a foul smell when your battery is over-charged
    And I would also get the alternator rebuilt

  7. ham308

    ham308 Formula Junior

    Nov 3, 2003
    NE Switzerland
    Full Name:
    Richard Ham
    If you fit the replacement alternator, it's cheap, it's all new and it's going to last along time so you can forget about it.

    As for uprating to more amps, it would depend on the running you intend to do. Cold mornings and short journeys are one thing. A good battery, good alternator and normal running, ( even with a woofer to blow the windows out :) ), no problem? .....

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