Seeking possible solution to altitude and ADSB out issue on my Garmin set up:
Dual G3X Touch (GDU 460) Version 9.52
GPS175 (Version 3.22)
GA 36
GTX35R (Version 2.80)
GSU 25 (Version 4.50)
GMU 11 (Version 2.20)
GHA 15 (Version 2.00)
This set up performed beautifully for over two years. During the Condition Inspection this year there were three possible sources for this current error.
1: A local avionics A&P outfit performed the 24 month pitot/static test and the transponder inspection. The "apprentice" did the actual work and he was rather rough in handling the GSU 25 unit (pulling it to the limits of the wiring and tubing connections then flipping it over). He also left the ESP feature of the G3X system turned on which had the system going crazy using autopilot trying to correct the perceived pitch angles during the testing.
2: I moved the GA 26X antenna that connects directly to the Primary Flight Display G3X out from inside the avionics bay (under aluminum and not getting a constant satellite connection) to under the cowling onto the same platform as the GA 36 antenna that provides WAAS GPS for the system.
3: The local avionics A&P outfit also installed the GHA 15 unit. The wiring connections were made at the GMU 11 removing the CAN-bus terminator as the GHA 15 pigtail had the wire loop to terminate.
From the very first flight after completing the Condition Inspection (mid May 2025) through today the XPDR box at the top of the G3X screen (to the right of the COM and standby COM boxes) will flash a yellow "NO ADSB" above the squawked code often and less often (but still often) it will flash a yellow "NO ALT" above the squawked code before returning to the white XPDR. Class C traffic control has not mentioned not having ADSB or Mode C information but I have pulled PAPR reports and they indicate errors in reporting. Exceptions are noted on NIC, NACp and SIL. Missing Elements has red under BAlt, as well.
On the traffic screen a yellow dot appears atop my own plane image with 00 under it and an audio alert saying that traffic within a quarter mile same altitude sounds when the "NO ADSB" in yellow replaces the white "XPDR" in the squawk code box. Even more odd is that I sometimes use ForeFlight on an iPad connected to a Stratus 2 (as a backup on longer flights) and it will occasionally have a popup message warning of very close traffic same altitude. So somehow the Stratus is picking up conflicting ADSB output.
G3X messages has sometimes given a message of "ADAHRS not receiving GPS data."
Both Flysto (taking info from my G3X data card) and FlightAware (using public ADSB data) show my correct and accurate location and altitude throughout all flights.
I'm baffled. The avionics A&P is very busy and has asked me to take screenshot photos of various menu screens while flying but to date no potential solution has been offered. Any suggestions on where I can continue troubleshooting this myself?
Dual G3X Touch (GDU 460) Version 9.52
GPS175 (Version 3.22)
GA 36
GTX35R (Version 2.80)
GSU 25 (Version 4.50)
GMU 11 (Version 2.20)
GHA 15 (Version 2.00)
This set up performed beautifully for over two years. During the Condition Inspection this year there were three possible sources for this current error.
1: A local avionics A&P outfit performed the 24 month pitot/static test and the transponder inspection. The "apprentice" did the actual work and he was rather rough in handling the GSU 25 unit (pulling it to the limits of the wiring and tubing connections then flipping it over). He also left the ESP feature of the G3X system turned on which had the system going crazy using autopilot trying to correct the perceived pitch angles during the testing.
2: I moved the GA 26X antenna that connects directly to the Primary Flight Display G3X out from inside the avionics bay (under aluminum and not getting a constant satellite connection) to under the cowling onto the same platform as the GA 36 antenna that provides WAAS GPS for the system.
3: The local avionics A&P outfit also installed the GHA 15 unit. The wiring connections were made at the GMU 11 removing the CAN-bus terminator as the GHA 15 pigtail had the wire loop to terminate.
From the very first flight after completing the Condition Inspection (mid May 2025) through today the XPDR box at the top of the G3X screen (to the right of the COM and standby COM boxes) will flash a yellow "NO ADSB" above the squawked code often and less often (but still often) it will flash a yellow "NO ALT" above the squawked code before returning to the white XPDR. Class C traffic control has not mentioned not having ADSB or Mode C information but I have pulled PAPR reports and they indicate errors in reporting. Exceptions are noted on NIC, NACp and SIL. Missing Elements has red under BAlt, as well.
On the traffic screen a yellow dot appears atop my own plane image with 00 under it and an audio alert saying that traffic within a quarter mile same altitude sounds when the "NO ADSB" in yellow replaces the white "XPDR" in the squawk code box. Even more odd is that I sometimes use ForeFlight on an iPad connected to a Stratus 2 (as a backup on longer flights) and it will occasionally have a popup message warning of very close traffic same altitude. So somehow the Stratus is picking up conflicting ADSB output.
G3X messages has sometimes given a message of "ADAHRS not receiving GPS data."
Both Flysto (taking info from my G3X data card) and FlightAware (using public ADSB data) show my correct and accurate location and altitude throughout all flights.
I'm baffled. The avionics A&P is very busy and has asked me to take screenshot photos of various menu screens while flying but to date no potential solution has been offered. Any suggestions on where I can continue troubleshooting this myself?
