I have a 912 ULS in my SeaMax amphibious aircraft. We were lubricating the landing gear, cycling it up and down a few times with the plane on jack stands over the weekend.

I obviously didn't want to run the engine so I connected an external 12V battery charger to the battery to provide power. The battery in this plane is not very powerful so it can't really handle much load like the gear cycling without running down very quickly. 

With the master on, we cycled the gear a few times then put everything back together. I then ran the engine and the voltmeter is showing almost 20V @ 4000 rpm. I shut down and am going to do the steps in this video:


... but my question is, could I have damaged the regulator/rectifier during this test? 

My working assumption is that I dislodged a wire during the testing process - everything in the SeaMax is difficult to get at and really tight and I'll know more soon, but in the interim, is the procedure I followed wrong? If so and if I've damaged the voltage regulator/rectifier, what could I have done differently to avoid damaging it?


  • Re: Voltage regulator over-voltage: what could have caused it?

    by » one year ago

    I doubt you did any damage. The charger may not have been able to keep up with the gear motor and the battery got run down. I would charge the battery charge the completely with an external charger and then run the engine and then see what you get. Do a continuity check on your regulator wiring in the meantime

  • Re: Voltage regulator over-voltage: what could have caused it?

    by » one year ago

    The "C" Lead of the regulator must be connected to the Battery during operation and disconnected when OFF: Usually through the MasterSwitch.

    If the "C" Lead becomes disconnected during operation, the regulator will be in an unregulated MAX Voltage condition.

    Check the wiring on the regulator; Especially the "C" Lead.

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated.

    Thank you said by: Matt Hocker

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