fbpx

 

What started as simply not getting CAN data from the Rotax to the Dynon in my new build/installation has become much bigger. Turns out that my ECU appears to be in a coma.

When measuring system amp draw, I'm only getting 0.35A when the Start or Backup switches are on, which is about what the fuse box is said to pull. The ECU alone is reported to pull 1.2A, so I'm a bit short.

I've verified and re-verified my wiring, even pulling ALL engine-related wires from the airframe and reconnecting only the bare minimum. I've checked and re-checked regulator A and B grounds and continuity in Start and Backup modes.

What I'm left with is some interesting discoveries in and around the fuse box:

First is the fact that only the B side is lit when in Start or Backup mode, but I think this is normal in a pre-start state. Please do look at the pics and confirm (might be hard to see, but greens are lit up, reds are not).

More interesting is that while the lugs from the fuse board to the regulator (red and two blacks) have 13v, the fat round yellow connector outside the regulator has 0v on any of its pins.

I don't know from where the ECU is supposed to get its juice, but the fuse box and B voltage regulator is a good guess, no? If there's power going into the regulator, shouldn't there be some coming out, into the wiring harness, and maybe on to the ECU?

Maybe I'm thinking about it wrong. But I'm otherwise kinda stumped.

PLEASE help. What do I check next?

9483_1_2022-10-07 13.57.41.jpg (You do not have access to download this file.)
9483_1_2022-10-07 23.58.34 Large.jpeg (You do not have access to download this file.)
9483_1_2022-10-07 23.58.52 Large.jpeg (You do not have access to download this file.)
  • Re: Need help troubleshooting a sleeping ECU

    by » 4 months ago


    The round connector with yellow wires won’t have power until the alternator (engine) is running, that is the AC voltage from the alternator to the rectifier/regulator.   I would start with the following tests, it sounds like you have done some of them, but work through them in this order.

    With ALL switches off:  Verify there is NO continuity between the two (A, B) regulator ground plates.

    With ALL switches off:  Verify there IS continuity between the regulator B ground plate and the airframe ground.
     
    With ONLY the Backup Battery switch on:  Verify there IS continuity between the two regulator ground plates.

    With ONLY the Start Power switch on:  Verify there IS continuity between the two regulator ground plates.

    With ONLY the Master Switch on: Verify there is 12volts on the X3 connector Pin 3 (horizontal pin) in reference to the regulator B ground plate (airframe ground).

    With the Master Switch AND the Backup Battery switch on:  Verify there is 12 volts on the X3 connector Pin 1, in reference to both of the regulator ground plates. 

    With the Master Switch AND the Start Power switch on:  Verify there is 12 volts on the X3 connector Pin 2, in reference to both of the regulator ground plates.  

     

     

     


  • Re: Need help troubleshooting a sleeping ECU

    by » 4 months ago


    Without a schematic of the Fuse Box it's hard to know precisely where to look, but I would also check continuity of fuses in the Fuse Box.  Given that the A side appears to be the trouble, I would suspect the 20A fuse (F20) next to the large "A+" stud, and the small green board-mounted fuse (F24) near the "A" and "A-" studs.  Perhaps also the 7.5A fuse (F3; in the path for "Selector Switch A") at the left-most end of the long row of fuses.  All fuses should be a dead short with your meter in continuity mode, or nearly zero ohms in resistance mode.

    This information is in the Heavy Maintenance Manual (64Mb PDF) chapter 76-10-00.  The Fuse Box section begins on page 29 (page 345 of the PDF).  Manual revision pages are here (5Mb PDF).


  • Re: Need help troubleshooting a sleeping ECU

    by » 4 months ago


    All 7 continuity and voltage checks done, I'm seeing the results that Jeff said to expect.

    All fuses Eric mentioned are good. I also pulled and visually inspected every other fuse in that row, even though the LEDs already indicated that they're good.

    Still no lights on the A side of the fuse box, and no ECU power draw. Is the A side supposed to be lit before engine start, or does that side only come alive after GenA kicks in?

    More ideas?

     


  • Re: Need help troubleshooting a sleeping ECU

    by » 4 months ago


    The LEDs on the "A" Generator do NOT illuminate before START.
    The ECU Power is sourced at the FUSE Box  X1(A) and X2(B) connectors and delivered to the ECU through the A1, A2 and B connectors.

    DO NOT go reseating the A1, A2, and B connectors without a VERY GOOD reason.
    They have a 20-reconnect Life Limit.


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


  • Re: Need help troubleshooting a sleeping ECU

    by » 4 months ago


    Bill Hertzel wrote:

    The LEDs on the "A" Generator do NOT illuminate before START.
    The ECU Power is sourced at the FUSE Box  X1(A) and X2(B) connectors and delivered to the ECU through the A1, A2 and B connectors.

    DO NOT go reseating the A1, A2, and B connectors without a VERY GOOD reason.
    They have a 20-reconnect Life Limit.

    Ok, that's really great to know. I can stop worrying about the A side of the fuse box.

    And yeah, my ECU connectors were installed on Oct 6 and haven't come off.

    So if my A side is fine, and my fuse LEDs are lit, which indicate that my ECU is powered up, why am I only seeing 0.35A total system draw with Start and/or Backup power on? Should I not see ~1.5A?

    This all started with a lack of CAN data on the Dynon, which I and Dynon deduced was a sleepy ECU. But Bill is indicating that the ECU and fuse box are fine, my voltages and continuity appear fine. But there's still the lack of amp drain.

    This is getting frustrating. I just want to see oil pressure on the screen so I can get on with my first engine start.


You do not have permissions to reply to this topic.