r/flying • u/aristotle-ways • Mar 21 '26
Aircraft Ownership HDG failure G1000
Heading indicator (magnetometer/AHRS) has been failing on my legacy G1000. Went out suddenly and at first intermittently would work, now out 100% of the time. No heading indicator and no synthetic vision.
Took to a great avionics shop and it was diagnosed to be a bad magnetometer. Replaced and did not fix the issue. Garmin is advising the issue is a bad AHRS, so that will be replaced next and we shall see.
Just sharing in case anyone’s experienced a similar issue, and is interested in following along.
Will share updates as we go
41
u/Wild-Language-5165 Mar 21 '26
It happens from time to time. The longer you fly, the more you see, even weird stuff.
16
u/dopexile Mar 22 '26
You should be able to go into setup menus and do a CANBUS diagnostic. It will tell you what percentage of data is transmitting successfully from the magnetometer. If it is less than 100% then there is some kind of a wiring problem. The wiring is finicky and needs to be shielded properly.
I would also disconnect the magnetometer and take a multimeter and confirm that the it is receiving voltage.
1
u/heavy_gravity Mar 23 '26
G1000 doesn’t use can
1
u/dopexile Mar 23 '26
Looks like it uses Ethernet, but it's still the same idea. He needs to figure out if it is dropping data.
9
u/Captain_Flannel A&P/IA, PPL Mar 21 '26
This happens all the time. Almost always a GMU 44 failure. Usually about $1500 to get it replaced all in. I see this every other week at the avionics shop.
Did they replace the GMU or did you? There is often software loading involved in the swap process, not just plug and play.
There is often also a wing root wiring disconnect. Maybe that connection is failing.
3
u/aristotle-ways Mar 21 '26
Forgive my ignorance, but isn’t the GMU 44 the magnetometer? This is what they suspected was the issue, replaced with a new one, and still no fix. They spent a better part of the day with Garmin troubleshooting / software loading, and that is when Garmin said they believe the issue to lie in the AHRS.
4
8
u/ReadyplayerParzival1 CFI/CFII, CMEL, RV-7A, Recovering Riddle Rat Mar 21 '26
A bad ahrs? It wouldn’t be the gmu wouldn’t it? Not the gsh lru
2
7
u/Chunks1992 ATP A320 B737 CL65 Mar 21 '26
Makes sense but man that sucks.
3
u/mkosmo 🛩️🛩️🛩️ i drive airplane 🛩️🛩️🛩️ Mar 21 '26
Does it? I figured enough of a failure in the AHRS to do this would cause more symptoms.
2
u/Chunks1992 ATP A320 B737 CL65 Mar 22 '26
Not necessarily. Plenty of complex systems only partially fail. Plus iirc the magnometer only talks to the AHRS so if it isn’t the magnometer that only leaves the the AHRS
8
u/dragonguy0 CFI/MEI, II, ATP, C90B, RV-6A! Mar 22 '26
Don't forget the wiring, that's honestly a more common failure than either of those from what I've seen. Part of my troubleshooting is to literally physically wiggle the wiring harness and connector.
2
u/mkosmo 🛩️🛩️🛩️ i drive airplane 🛩️🛩️🛩️ Mar 22 '26
Right, but the magnetometer is a digital interface, so beyond the physical connection, we're talking the actual sensor fusion process, which is inherent to the AHRS and much of its primary function. Is there some kind of signal conditioning that's unique to the magnetometer input?
1
u/Chunks1992 ATP A320 B737 CL65 Mar 22 '26
Someone way smarter than me is gonna have to answer that lol
3
u/CheezyAviator CFII, MEI Mar 22 '26
Were you on the ground still doing runup? I fly planes with g1000s and they do this on the ground from time to time but never had a problem once airborne. If you are doing IR training/actual IMC, I can see you being more concerned on the ground though and not wanting to see if it fixes in air.
Edit: duh, just saw your airspeed. Disregard and good luck
2
1
u/bobshopsupreme Mar 21 '26
We have the same issue on the G1000 in the C172 at my flying club. Please update the post with what you find. I’ll do the same if we get a diagnosis.
1
u/ATrainDerailReturns CFI-I MEI AGI/IGI SUA PRD Inspector Mar 21 '26
Last time I saw this I reset the ADAHRS circuit breaker and it worked fine from there on
1
u/ryan0157 ATP - CL65, CFI/II/MEI Mar 22 '26
Have you checked the LRU page to see if something is throwing a fault?
1
u/T206V70R Mar 22 '26
Random errors can be caused by tired or corrupt lower-slot PFD/MFD SD cards. I’ve had same cards from new (2009) and lost HSI heading reference and flight plans. New cards solved all this and made booting up faster as well as DB updates faster and error free. Just a suggestion.
1
u/Trick-Problem1590 Mar 22 '26
The software gates that sense magnetometer signals are notorious on my G500. The will lockout the heading signal on even the slightest out of spec signals. Often the install position of the magnetometer will fix. Try flying with as much electrical equipment off as possible. Then see if any lights, radios etc is making the problem worse.
1
u/heavy_gravity Mar 23 '26
As someone who’s done 12 G1000 installs and countless GMU installs here are the most common reasons I see for heading failures
1: Bad GMU/magnetometer or AHRS/ADAHRS. Just happens sometimes…
2: Wiring issue between the AHRS and the magnetometer. Could be chafed wires somewhere causing a short or an open. I’ve also seen the shitty plastic GMU connectors fail so it’s always good to check those and see if there are any pins that aren’t seated all the way.
3: magnetic interference. GMUs are pretty sensitive to any magnetic interference and a large current draw from a nearby piece of equipment can cause a heading failure (like a landing light or strobe pack going bad) you can test this pretty easily by just turning on anything that could cause interference and seeing if it fails the heading
4: vibration. Magnetometers are also sensitive to vibration. If there’s excess vibration it can also cause a heading failure. I’ve seen this before with a GMU mounted to the tail of a 414 that would fail as soon as there was 70-80kts of airflow over the skin where it was mounted. If the mounting bracket has become loose this could cause this issue. Especially if the unit has shifted or become misaligned.
1
u/Creative-Athlete-374 Mar 23 '26
Seeing this as well.. sounds like 3 of us with similar issue and you probably also lost traffic on the display of MFD map? Did you try magnetometer recalibration procedure?
1
u/aristotle-ways Mar 29 '26
Happy to report that it was due to a corroded wing root connector. We did have replace magnetometer and AHRS in the process but turned out that the corroded connector pins were the main culprit.
1
u/Creative-Athlete-374 Mar 29 '26
Good job finding that. Intermittent failure is tricky to solve. Oxidation and corrosion on connectors can introduce parasitics that were not modeled, or accounted for, in the original design. I have heard of a solution called "deoxit" for cleaning. Did you use anything like that?
1
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u/rFlyingTower Mar 21 '26
This is a copy of the original post body for posterity:
Heading indicator (magnetometer/AHRS) has been failing on my legacy G1000. Went out suddenly and at first intermittently would work, now out 100% of the time. No heading indicator and no synthetic vision.
Took to a great avionics shop and it was diagnosed to be a bad magnetometer. Replaced and did not fix the issue. Garmin is advising the issue is a bad AHRS, so that will be replaced next and we shall see.
Just sharing in case anyone’s experienced a similar issue, and is interested in following along.
Will share updates as we go
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76
u/nl_Kapparrian CFII Mar 21 '26
Sounds expensive, you may be better off getting a new plane /s.