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I have a Tecnam P2002 EA Sierra with a Rotax 912 ULS. Only recently acquired and my first flight was a few days ago.

When the ignition is switched on, the alternator light does not illuminate as I would expect. I have checked the bulb and this is good.

Engine start all good and flight over 2 hours also with no issues and voltmeter shows about 13 volts whilst airborne.

So it appears that the battery is being charged, but any ideas as to why the light does not illuminate on the ground before engine start with ignition on and then extinguish after start as per normal?

 

Thanks.

  • Re: Alternator Light

    by » 3 months ago


    Take a meter and verify one side of the bulb is getting 12 VDC and the other side is wired to L on the regulator.

     

    Rotax Electrical Charge System & Ducati Regulator [Archive] - VAF ...


    Thank you said by: RotaxOwner Admin

  • Re: Alternator Light

    by » 3 months ago


    Thanks for your advice. I'll try this.


  • Re: Alternator Light

    by » 3 months ago


    You can see the diagram of the operation of the "L" terminal (either with a lamp or with a led)
    To check and test the regulator's "L" terminal, first measure that the regulator's ground is properly connected to the negative pole of the battery. The mass of the regulator must be "faultless"
    Also check all the terminals of the regulator connector, this connector has often caused many problems ...
    switch off all avionics which could consume excessively current, due to a fault
    If the LED or lamp remains On with the engine running above 2000 RPM, stop the engine and disconnect the "L" terminal
    Then place an Ohmeter between terminal "L" and the regulator earth. if you measure a very low resistance (see zero) the Mosfet transistor of the regulator is dead ... And it is not repairable other than by changing the regulator ...
    You can do a final check:
    disconnect the old wiring from the "L" terminal.
    Connect a lamp or a led (with its resistance) as on the diagram, directly on the positive terminal of the battery and on the terminal "L", without connecting anything on the negative terminal of the battery.
    (One wire on the positive of the battery and the other on the terminal "L", with the lamp or the led in between)
    The lamp or led should light up
    Start the engine and test at 2000 rpm (or more), the lamp or the LED should go out.
    Take this opportunity to measure the charging voltage, which must be greater than 12V (approximately 13V5 - 13V8 depending on the state of the battery)
    If the test works well, test lamp off when the engine is running, check the wiring of your charge light, or even better, change it.
    Beware of a lamp holder that can touch the ground of the plane, because poorly insulated.
    One last thing useful for all, when you find the fault, tell us what it was!

    26733_2_Schma 22L22 connection.png (You do not have access to download this file.)

    Thank you said by: RotaxOwner Admin

  • Re: Alternator Light

    by » 3 months ago


    Jacques, appreciate your thorough reply, thank you.

     

    I will follow your instructions and be certain to post my findings within a week.

     

    Thanks again.


  • Re: Alternator Light

    by » 3 months ago


    Here are my findings about the alternator light not illuminating with ignition.

     

    The previous owner had 2 red lights fitted. One labelled Alternator and the other labelled Starter Engaged Light.

     

    Once I began testing the circuit, it became clear to me that he has labelled the lights incorrectly!!

     

    The starter light is actually the alternator light and vice versa.

     

    So basically the lights have never worked in the correct manner.

     

    How strange!!

     

    I've now swapped the labels.

     

    Thanks again for your advice.


    Thank you said by: RotaxOwner Admin

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