Home Forums General Technical Help Dynamo Good Voltage but …

This topic contains 4 replies, has 2 voices, and was last updated by  JAN 4 minutes ago.

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  • #63875

    brianw
    Participant
    Club Member

    Dynamo test … take off its wires .. connect a link wire between D &F  measure voltage at tick over …. 15 v rising quickly with revs , so according to the haynes manual that seems “working”  .    But connected up, the thing struggles to get above 13.6v  day time  &  12.0 v with lights on ( depleating battery) ,   measured at the battery running at 50mph.     Inside the dynamo the brushed are good , BUT the commutator is worn.

    ( connections wires & control box connections seem ok)

    Is it “a known thing” to have a dynamo that passes the “no load” voltage test, but when it comes to using it produces very little power ?

    #63876

    JAN
    Participant

    Suspect regulator, the test proves only the dynamo.

    #63877

    brianw
    Participant
    Club Member

    .. thanks .. will investigated

    #63899

    brianw
    Participant
    Club Member

    Regulator box appears working ….  The Wiring diagram in my haynes manual shows  wiring   ” D Dynamo to Regulator, A Regulator to Battery, A1 Regulator to ignition/lights”

    My 67 regulator doesn’t have an A1 terminal & is wired ” D Dynamo to Regulator, A Regulator to Battery, then Battery to ignition/lights”  This means the full lighting/ignition current flows in the A wire.    I doubled up the  “A Regulator to Battery” wire & got an extra 0,5 to 1 volt at the battery

    ( in the diagrams A & A1 are drawn connecting  across a coil , not sure what this is for ?)

    Question for people who did Alternator Conversion …. Where did you run the  Alt to Battery wires …   ?

     

    #63900

    JAN
    Participant

    “Regulator box appears working…” What indicators do you have to arrive at this conclusion? You know the dynamo output will exceed 15V but something is reducing that voltage to below the charging rate. The only thing that can do that is the regulator.

    The dynamo contains a weak permanent magnet. When the engine turns the dynamo quickly enough, this will produce a very small current from the armature, which is fed to the regulator. The regulator returns this small current to field coils within the dynamo, producing a much stronger magnetic field. This in turn produces a much greater output from the armature to the regulator, and so on; the output will simply rise higher and higher as rpm increases, which is what the test did. The regulator’s job is, once the output reaches the optimum level, reduce the current returned to the field coils and thereby limit the dynamo’s output. A faulty regulator coupled to a healthy dynamo will cause the latter to either over-charge or under-charge, or not give any output at all.

    The main alternator connection(s) can go directly to the battery; to the live side of the solenoid, or you can do as I did and link the D and A or A1 terminals of the regulator, at the same time disconnecting the earth lead.

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