Alternator or ??? Part Deux | FerrariChat
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Alternator or ??? Part Deux

Discussion in 'Technical Q&A' started by enjoythemusic, Aug 26, 2005.

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  1. enjoythemusic

    enjoythemusic F1 World Champ

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    #1 enjoythemusic, Aug 26, 2005
    Ok, here is the problem more defined. On the dash of the 308 the battery light comes on at times. It seems to matter not the voltage as it comes on if the battery reads 13.2V or 12.7V, but will also go OFF at 12.7 and 13.2V. It basically will light bright red at times, flicker at others, and be off for others without rhyme/reason...

    BUT...

    It appears that at rpm over 3.5k it tends to light up or go to a brighter light from flickering.

    It appears to light up when the radiator cooling fans turn on.

    So it seems when more amperage is needed it lights up. What i did was put a new end connector on the positive battery wire. i checked and cleaned the grounds. Today i am replacing the battery with an Enersys lightweight battery and will replace the negative cable wire terminal as well.

    My wondering is, the only reason seems to be the light comes on when more amperage is needed so... bad connection? Or perhaps the alternator is going bad slowly, or ???? The battery does seem to be charging and not draining out.

    FYI: Voltage readings were done with the Pioneer AVIC-1 radio/GPS unit that has a built-in digital meter.

    Maybe it is a relay???????????????? Or ?????????????? Have i missed something or am i trying to save $$$ but not admitting the alternator is going bad and that means $xxx to fix + labor hours?
     
  2. Verell

    Verell F1 Veteran
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    #2 Verell, Aug 26, 2005
    Last edited by a moderator: Sep 7, 2017
    SO SORRY:
    The light (circle with an X in it in schematic) is really an 'alternator output' light, it does NOT reflect battery voltage. It is directly connected to the alternator (lighter gauge green wire with spade connector). The alternator's regulator senses the alternator's output voltage, & the light is on when the 3 internal diodes connected to the alternator side of the light are not generating enough voltage for alternator's voltage regulator to keep the alternator's internal field coil excited.

    Other than anoverload, there's almost nothing external to the alternator other than low engine speed that can cause the light to go on.

    A bad connection outside of the allternator would add resistance in the output path which would actually tend to decrease the load on the alternator.

    IMHO, your alternator has a bad regulator, a bad diode, or one of the coils has gone bad. You could pull the alternator & take it to a shop for them to test it. The shop can generate a graph of output current vs shaft RPM.
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  3. sparta49

    sparta49 F1 Veteran
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    #3 sparta49, Aug 26, 2005
    Steve I replaced the alternator on my ex -308 with a new Bosch one from Gt Car PArts for around $200 from what I remember I wasn't that labor intensive to replace . Now the ordeal I just went through with the Nippo unit on my 348 was another matter entirely :)
     
  4. Ken

    Ken F1 World Champ

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    #4 Ken, Aug 26, 2005
    This is typical of the voltage regulator starting to go. When people give me crap about having an ammeter (as opposed to a volt meter), I tell them that I get plenty of warning when the alternator is going, you don't. Well, your case refutes that! The red light's theatrics are the same as my meter reading in the - all the time.

    You can replace the VR in the alternator yourself; mine cost $19. If you can get a Delco/Bosch etc. part # it may cost about the same. The only tricky part is reloading the brushes but it's easy when you know how! You are presently running off the battery and that won't last too long.

    Ken
     
  5. Verell

    Verell F1 Veteran
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    #5 Verell, Aug 26, 2005
    Because it's located so far from the battery, the 3x8 regulators are a non-std voltage. They need to be replaced with an exact match replacement, not a 'universal' one.
     
  6. Ken

    Ken F1 World Champ

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    #6 Ken, Aug 26, 2005
    That's too bad! If the cable is heavy duty enough, it *shouldn't* make a difference though. Several Europa owners have moved their battery to the front compartment and they have no charging issues; they do stress to use heavy gauge cable. Of course, this may cost more than the correct VR.

    Ken
     
  7. Verell

    Verell F1 Veteran
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    #7 Verell, Aug 26, 2005
    The cable is plenty heavy, about 10mm thick braided copper like welding or monster cable.

    Don't have my log handy, wasn't a big diffeence, but when I had my alternator rebuilt, they had to special order the regulator think it cost me about $40 4 years ago.
     
  8. enjoythemusic

    enjoythemusic F1 World Champ

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    #8 enjoythemusic, Aug 26, 2005
    Thanks everyone, just as i felt. As for running off the battery, this thing has been going on for about a month on and off and have driven well over 2,000 miles. Yes i would check the battery each time i got home and the 'better' 2A/10A Schumacher charger with analog gauge and it would always say the battery is fine, no need to charge it (and yes, i would leave it attached for 15 minutes before making sure all was fine).

    Drove back from Lime Rock Park (5 hours) and no problems. Drove the the beach yesterday (70 miles each way) and no problems. Then there was the track day at NHIS (300+ miles total) and no problems.

    THIS is why i am SO perplexed, but yeah she is ready to go. Guess today was an interesting day, i installed a lower reserve battery so this should make driving.... very interesting :)

    Thanks again everyone and she will be repaired in early September with other upgrades.
     
  9. Verell

    Verell F1 Veteran
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    #9 Verell, Aug 26, 2005
    My swag is that you're still getting charging a high enough % of the time to keep your battery charged. Be interesting to see what you experience with the lightweight battery.
     

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