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Thread: Garmin G3x Wiring Questions

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  1. #1
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    Default Garmin G3x Wiring Questions

    Hey everyone! Working on wiring and my brain hurts! I am going to have lots of wiring questions so I figured I should start another thread instead of on the build log?


    I am currently working on wiring up the gea-24, which is the box that all the engine senors connect to. The manual shows (I think) a 2 conductor wire coming from the CHT to the GEA-24. It is saying most of the sensors, other than the egts, need to have Garmin Shield block ground, which I assume is grounding the shield to the backshell? Also with lots of sensors needing to be grounded to the backshell do you just start stacking the grounds? Lastly it shows the 2 conductor wire going to each CHT. One as the signal and the other grounded to the aircraft. It is showing the ground to be on the end where the CHT probe is? Not sure what you do there? Is it okay practice to run a single shielded wire from the CHT probe to the GEA-24 that then the shield is grounded at the backshell of the GEA-24, and then run another shielded wire from the GEA-24 for that CHT to the ground bus for the aircraft?

    Sorry I know there is a lot of questions there, any input would be helpful!
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  2. #2
    Senior Member Flybyjim's Avatar
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    Default Re: Garmin G3x Wiring Questions

    Hi Dustin,

    After reading the manual setup I had the harness made for my whole G3X system, this is one area I felt it was better to have someone build it that did it every day. I used Steinair for this service.

    Jim

  3. #3
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    Default Re: Garmin G3x Wiring Questions

    I know the feeling! Seems like I need to just hire someone to come out and wire it all up for me🙂
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  4. #4
    Senior Member PapuaPilot's Avatar
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    Default Re: Garmin G3x Wiring Questions

    No, it doesn't need any kind of keep alive power.

    Most of the LRUs have 2 pins so you can power it from 2 sources if you desire.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

  5. #5
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    Default Re: Garmin G3x Wiring Questions

    Quote Originally Posted by PapuaPilot View Post
    No, it doesn't need any kind of keep alive power.

    Most of the LRUs have 2 pins so you can power it from 2 sources if you desire.
    Thanks! My "reading" is not so bad.........my "recall" not so good
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  6. #6
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    Default Re: Garmin G3x Wiring Questions

    Who knows the gtx45R? From what I am gathering, RS-232 (1) is used for GSU-25(adahars) RS-232 (2) is for the GDU 4xx (G3X touch screen). Do I just use RS-232 (3) for the GPS 20 input?

    I guess what I am asking is I am running the GPS-20, which is providing wass gps signal to the transponder. Isn't the transponder going to use waas gps position and altitude from the transponder? So do I still provide info from the GSU-25, which is providing altitude via static pressure?
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  7. #7
    Senior Member Flybyjim's Avatar
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    Default Re: Garmin G3x Wiring Questions

    Steinair was a great company to work with, very patience and helpful. I am going to be painting this fall and hope to fire up the panel before year end.

  8. #8
    Senior Member efwd's Avatar
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    Default Re: Garmin G3x Wiring Questions

    Don't be fooled by the belief that the shop has people who do it everyday. You might be surprised, as I was. Go with Stein Air. They sponsor this site too.
    Eddie Forward
    Flying
    SS7, 912iS, Garmin G3X

  9. #9
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    Default Re: Garmin G3x Wiring Questions

    Hi Eddie! Yeah I think I am going to charge forward trying to figure this out. Looking back I think I would have gone with AFS or Dynon pre-wired panel from Stein Air. I feel like I am too deep to look back now. Eddie did you run your CHT sensor wire to the probe? The drawing has me to believe the CHT probe is grounded next to the probe itself on the engine, but I dont see why I can't ground the sensor at the ground bus bar coming from the GEA-24?
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  10. #10
    Senior Member PapuaPilot's Avatar
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    Default Re: Garmin G3x Wiring Questions

    I'm not totally sure I understand all of your questions, but this may help.

    The GPS-20A is your WAAS GPS source required for ADSB-out position and possibly IFR navigation. It's not the altitude source for the transponder as GPS altitude is not overly accurate. The altitude source for the transponder/ADSB and the display(s) (GDUs) comes from the ADAHRS (GSU-25). The GSU-25 provides pressure altitude, which is corrected using the altimeter setting and is very accurate.

    I'm not sure how all of these hook up and communicate with each other with the GTX-45R. I have a different transponder. My GPS-20A connects directly to the transponder using a RS-232 channel and sends its data on the CAN bus too. The CAN bus connects to both the GSU-25 and GDU-465. Therefore using both the CAN bus and RS-232 the WAAS GPS position is provided to the entire G3X system.

    You are going to need to look carefully in the installation manual chapters 26 and 27 to find the answer to this.
    Phil Nelson
    A&P-IA, Maintenance Instructor
    KF 5 Outback, Cont. IO-240
    Flying since 2016

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