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  • Re: Flashing Lane Lights

    by » 7 years ago


    Yes Rob all relay blocks are solid. As the three are identical items I tried changing them round but it made no difference, which may suggest the problem is in the circuit board not the relays.

  • Re: Flashing Lane Lights

    by » 7 years ago


    ...With connectors coupled
    Looking down on the fuse box terminal posts, receiving the regulator/rectifier cables numbering from left to right 1-6, A on the left and B on the right.

    Engine running circa 2000rpm direct voltage
    Between 1&3 14.3volts
    Between 2&3 14.3volts
    Between 4&6 14.05volts
    Between 4&5 2.9 volts <---<<< ???



    The problem may be in the regulators.
    Other than the color of the connectors it would be reasonable to assume that they are identical.
    There is a difference in the way the grounds are connected, so take pictures beforehand if you decide to try a swap.

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


  • Re: Flashing Lane Lights

    by » 7 years ago


    Hi Bill I have rerun and produced anther set of voltages off the fuse box terminals. The second values are with the regulator A&B 3 pin connectors switched, which shows to my mind that the regs. are OK. The odd voltages between terminals 4 & 5 persist although, they have increased slightly.
    Engine running circa 2000rpm taking it up to 2600 makes no difference
    Between 1&3 14.3volts : 14.3volts
    Between 2&3 14.3volts : 14.3volts
    Between 4&6 14.05volts : 14.05volts
    Between 4&5 5.4 volts : 6.5 volts

    Apologies Bill, the above statement, re regulators status is inaccurate, the exercise proves the generators not the regulators. I will trial with switched regulator outputs asap.

  • Re: Flashing Lane Lights

    by » 7 years ago


    -Hi Bill
    I have rerun and produced anther set of voltages off the fuse box terminals with the regulator outputs switched and it shows that the regulator/rectifiers give similar outputs, 14+volts and have a clean bill of health..
    I have looked more closely at the wiring into the box. There are 6 terminals labelled by Rotax as X4 through to X9, X4-X6 serving the EMS ground, side A and X7-X9 serving aircraft ground, side B.

    Off the drawing, X5 and X6 are common source whist X8 and X9 are not. I get between 4-5volts across these terminals (my old 4&5) and am not understanding why.

    The drawing has not reproduced properly X5 is attached to the ground plate.
    FuseboxTerminals_2018-03-28.jpg (You do not have access to download this file.)

  • Re: Flashing Lane Lights

    by » 7 years ago


    I have tried to reverse engineer the fuse box.
    It is difficult with the relays installed, Mine are NOT unpluggable.
    From what I can tell, the "A" side ground terminals have a connection to one of the relays.

    Here is what I think.
    If the A side fails, it is taken out of the circuit and the B side takes over.
    The B side is either connected to the ECU or the Airframe, so it always sees a load.
    When the A side fails it can be isolated and disabled by removing the grounds.
    That is why the ground paths look different.
    They are equivalent when the relay is closed and all is operating normally.

    Are you measuring these voltages with the engine running?

    Rotax will not discuss the operation of the fuse box internals.
    I have requested a schematic and they want to keep it confidential, Factory info only.
    The fuse box is considered a single non-reparable item so even the dealers cannot get the info.
    The fuse box is to be considered a single component and replaced as such. Nor repairs allowed.

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


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