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This is for the 3x drivers.
Been dealing with the AHRS NOT RECEIVING MAGNETOMETER DATA amber flag and HDG for a year now.

The aircraft delivery was delayed due to this reason. Then it has been continual off and on issue.
Mandy and "engineering" don't have a fix so this is frustrating. We are going through the same motions again and performing the 3X GPS alignment process spinning the aircraft around 360 degrees on the ground to get oriented. You are supposed to be using a compass rose. We do not have one at our airport so using handhelds gps and iphone compass. We'll fly to another airport with a compass rose next.

Details:

Battery power up (away from hangars or interference) - AHRS amber flag on 3x, shows AHRS NOT RECEIVING MAGNETOMETER DATA.
Headings between small attitude indicator heading at bottom and on 3x between 10-40 degrees off.
Engine power up, may stay the same or at best improve to about 6-10 degrees split on headings, amber flags usually stay illuminated.
Taxi out - may or may not correct itself and align.
Airborne - may or may not correct itself. It if does correct itself, it usually is only for a short period of time.
When AHRS flag illuminated airborne, setting a direct-to can show GPS course up to 25 degrees off actual course.

Anyone else having 3X AHRS issues?

Greg

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Have you gone into the configuration menus to make sure the magnetometer is communicating via the CAN bus?

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Yes.
It is not communicating. That is is the issue and we've been down the path with Icon on every part involved. Mechanics testing every single fitting and connection.

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Sorry to ask a simple question but in checking the connections did they actually ring out out the wires? Chaffing and poorly crimped connections can be a thing. Anyway Its a pretty simple troubleshooting step. Check that CAN HI, CAN LO, Shield Drain continuity between the GMA 11 and the G3X main connector. Make sure there is power, ground as well to the GMU 11.

Here is the CAN bus wiring (below) I can't seem to find the power wiring for the GMU 11 on the Icon maintenance manual. You might call ICON for that. That said they should be able to help you with all of this but from the sounds of it, apparently not. I've been gone for 2.5 years and I used to do a lot of wiring troubleshooting when the service team couldn't.

Anyway you should have continuity between:

• GMU 11 Pin 1 to GDU450 Pin 46
• GMU 11 Pin 2 to GDU450 Pin 45
• Back shell of GMU 11 and Back shell of GDU450 (G3X)
  
  Here is the diagram:

The only other thing I could think of is if you have continuity between the LRU's is to connect a CAN bus reader and see if you can get message traffic. I have had good luck in the past on that but never tried that with Garmin units. Might take some Guess and check on CAN 2.0 A or B and what Baud Rate its running at but shouldn't take too long to figure that out.

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Greg, I had this exact problem with my first G3X, turns out it was all because I used a "snap mount" to hold my GoPro in the cockpit. A snap mount is a heavy duty magnet holding device. It screwed up my magnetometer. Once we isolated it and figured it out (and removed it) all worked perfect. I doubt you have same problem, but thought I would share.