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Have reached the point where I have hooked up the 912is as it is shown in the Kitfox manual which electrically corresponds with the Rotax Installation Manual.  The bad news is that it doesn't appear to be working as I think it should.  I am using a G3X and have wired the FADEC CANBUS as called out in the Garmin instructions.  When I turn on the battery and then the Lane A and B switches, the A and B LEDs are non-responsive as in no flicker or anything.  I saw an earlier post by Eric Page talking about the 1.5K resistor being the wrong size (1.5ohms versus 1.5K) which loaded down his lights.  Checked my resistors and they are correct; 1K inline and 1.5K parallel to the LED.  I looked at my G3X and the Rotax FADEC is grayed out (doesn't see it) so am thinking that my ECU is out.  Saw a post somewhere talking about having a similar issue and when either the Start Power or the Back Up Power switch was selected, it all woke up (but unfortunately didn't have a description of what the issue was that I can remember).  So I tried that and with the exception of the Lane A and B lights still not working as expected, the system appears to connect with the G3X (i.e. The FADEC is no longer grayed out and when selected, shows that is indeed talking to the engine with all the pertinent information and can see the proper engine instruments show up.  Also interesting is that when I switch the Lane A and B switches on and off, the correct engine instruments controlled by those two lanes go on and off as well).  The minute I put the switch back into the center position, the FADEC disconnects and grays out again.  There is the three pin power switch on the fuse box and I have checked that.  Pins 1 and 2 power as advertised when the Start Power/Back Up switch is switched.  Pin 3 has 12VDC on it at all times.  So the bottom line is that the system appears to be acting like it's losing power or ground.  I have checked the switching ground side of the Start Power/Back Up switch and it too is working as advertised.  The Lane A and B sides are indeed isolated ground wise from each other till to flip the Start Power/Back Up switch which since that causes the FADEC to work, makes me think there is a ground issue.  The B side is grounded to the airframe/engine.

  • Re: 912is Wiring

    by » 12 months ago


    Gary,

    Much of what you are experiencing is actually correct.  When the engine in not running, neither Lane A/B, nor the CAN signal to the G3X will work unless either the start power or the backup power switch is turned on. During the normal start procedure the start power switch routes airframe power to the ECU, fuel pumps, spark, and injectors until the engine starts and the alternators take over.  Initially, when the engine first starts, alternator “B” powers the engine, then once the engine reaches 2500 RPM for a few seconds, alternator “A” takes over engine power and alternator “B” is then connected to the airframe buss. This is all automatic, and the start power switch is only needed until the engine starts, then it is turned off to isolated the engine electrical system.  The idea is that once running, the engine is electrically isolated from the airframe (with start power and backup power switches off) so that an airframe power problem can’t affect the engine.  

    So, if we take the lane lights out of the equation for now, you may not be as far off as you think.  If the lane associated instruments show up on the G3X when you switch each lane on (with start power on), the lanes are likely functioning. Maybe all you need to do is troubleshoot the lane lights.  


  • Re: 912is Wiring

    by » 12 months ago


    Jeff - Thank you for the response.  While 'thinking' I knew all that, it really helped to see it laid out like you did.  I think you are exactly right - the day's chore will be to look at the lane lights again.  Thinking that the Lane lights not working correctly got me going down the rabbit hole of "it's broken".   I got the Heavy Maintenance manual and looked up the fuses that control the lanes so I have those to check and I have some extra LEDs so I am going to wire those straight into the HIC connectors and see if they act differently.  Again thanks for the inputs.

    G


  • Re: 912is Wiring

    by » 12 months ago


    Gary, 

    I figured you knew most of that, but I found it hard to make my point without reviewing it.  You could use a meter across the 2/8 pins on HIC A and 2/10 pins on HIC B to see if they are working.  And remember they will only get power a couple seconds after being turned on until the lane initializes (sorry to state the obvious).  Also, I would check that you have the polarity correct on your lane LEDs.   


  • Re: 912is Wiring

    by » 12 months ago


    Jeff Blakeslee wrote:

    Gary, 

    I figured you knew most of that, but I found it hard to make my point without reviewing it.  You could use a meter across the 2/8 pins on HIC A and 2/10 pins on HIC B to see if they are working.  And remember they will only get power a couple seconds after being turned on until the lane initializes (sorry to state the obvious).  Also, I would check that you have the polarity correct on your lane LEDs.   

    Well Jeff you got me through it.  Thank you again.  The culprit?  "Also, I would check that you have the polarity correct on your lane LEDs." I would have sworn that I had checked the polarity of those LEDs (multiple times over the last week) and the heck of it was that I checked them again this morning and swore I had it right.  Out of frustration, I clipped and swapped the feed wires just to see what the heck.  Lo and behold, Lane A started working as expected.  All good.

    G


    Thank you said by: RotaxOwner Admin

  • Re: 912is Wiring

    by » 12 months ago


    That’s great Gary, the polarity on the LEDs is an easy mistake.  I’ve never flown a Kitfox but I hear they are fantastic.


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