Alternator & regulator question | FerrariChat

Alternator & regulator question

Discussion in '206/246' started by pshoejberg, Apr 6, 2017.

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  1. pshoejberg

    pshoejberg Formula 3
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    Peter H
    #1 pshoejberg, Apr 6, 2017
    Last edited by a moderator: Sep 7, 2017
    I suspect that I have connected my alternator the wrong way around! Maybe some of the skilled persons within the field of electronics can advise me a bit here? The picture below is showing the back of my alternator and there are three connectors. The red-circled "bolted" connector is obvious for the main power cable going to the cars battery via the terminal post on the fuse board. However, the two other connecters confuses me a bit. I assume one is the field and the other one perhaps ground. Can anyone please advice? In addition, I need to know if it necessary to ground the alternator / connecter?
    Secondly, I plan to upgrade the car with an electronic regulator of the type shown on the last picture. Is it possible to change out the old electro mechanical devise with this transistor-based unit?
    Thanks in advance
    Peter
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  2. dgt

    dgt Formula 3
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    #2 dgt, Apr 6, 2017
    Peter,
    Originally the Alternator did not have the 3rd termial inside the white housing next the to main output "bolted"connector. On our cars this was blank (... I believe this is correct!)
    This is a sense wire used on later (different) models connected all the way back to the battery.
    It was probsbly added when the alternator was rebuilt.
    You can connect this to the + terminal at the junction box on the firewall and it should work ok if the wiring is in good shape.
    The bottom one is the field which is part of the brushes.

    I had the same issue with a Fiat Dino alternator rebuilt as a spare which had the extra terminal.
    Regards Andrew
     
  3. pshoejberg

    pshoejberg Formula 3
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    #3 pshoejberg, Apr 7, 2017
    Thanks for the clarification Andrew. That might explain why I don't see much charging from the current setup since I have connected the "white" as the field and left the bottom most blank......This is then an obvious mistake. You mentioned that I must / can connect this "sense" connector to the cars +12V voltage system. I do not have +12V in my alternator junction box (L-series car), However I have +12 V at engine bay light and at the ignition and several other places. Is it ok to hook up the "sense" connector to one of these places?

    Finally, from looking at the cars electrical diagram, I see that the alternator is grounded...Is this done in practice or is he alternator grounded through the engine?

    regards

    Peter
     
  4. Ferrari27

    Ferrari27 Formula Junior

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    #4 Ferrari27, Apr 7, 2017
    Alternators would usually go to ground via the casing, the mounting and then through the engine. Only if the alternator is mounted on rubber bushes is a physical link needed. On boats where the engine would not usually be grounded things are a bit different. On your picture, if you look at the screw which holds the brushes in, it connects one brush to the alternator casing and therefore to ground. The other connector on the brush holder is at the opposite end of the circuit created by the brushes, the slip ring and the rotor windings.

    It is a very long time since I needed to know this stuff and someone with a knowledge that is greater than my memory will be able to provide more information but your new regulator should work. It may need a slight modification to the wiring though in order for the dashboard warning light to work (if there is one). Also, if you need to put in any additional cables to the extra connector on the alternator you probably need to ensure that it is switched via the ignition and not live all of the time.

    Robert
     
  5. pshoejberg

    pshoejberg Formula 3
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    #5 pshoejberg, Apr 7, 2017
    Thanks for input to all. I have now swapped the wire and the alternator is charging. However not much in idle, but 13.5V at 2000 rpm upwards. I did not install the extra wire to the "sense" sensor due to lack of access with the wheel well and exhaust manifold still in the car. Also tried to hook up the transistor based regulator with no success......I wonder if anyone have tried this conversion before?

    Best regards

    Peter
     
  6. dgt

    dgt Formula 3
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    #6 dgt, Apr 7, 2017
    Oops - I gave you bad info. The extra terminal isn't a reference that needs to be connected, it should be left disconnected.
    It's a half voltage (~7V) reference tapped off the alternator stator which is used on some cars to run accessories when the engine is running. It's not used on our Dinos so it sounds like you have the field correctly plugged into the connector on the brushes and charging.

    Regards, Andrew
     
  7. Ferrari27

    Ferrari27 Formula Junior

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    #7 Ferrari27, Apr 7, 2017
    If you have changed the alternator for a different one, have you also changed the pulley that drives it? If you have, and the new pulley is larger (I think!) than the original one, then at low engine speeds the alternator may not be turning fast enough to produce any charge.

    Robert
     
  8. pshoejberg

    pshoejberg Formula 3
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    #8 pshoejberg, Apr 7, 2017
    Thanks for the good news Andrew. That means I do not need to worry about that extra wire! I still have the original pulley, so speed is not the culprit when it comes to the idle low charge level. Perhaps the 48 years old mechanical regulator has a negative influence?

    Best Peter
     

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