G1000 AHRS failure?

[Robert C.]

Hi gang,

Had planned a leasurely luncheon run today...pre-flight, start....and oops, G1000 presents me with 2 error messages, no SVT and the HDG indication "crossed out." Error messages were:

• HDG Fault: AHRS1 Magnetometer Fault has occurred
• Traffic Fail: Traffic Device Failed

on the Aux page I get nice red "X" letters instead of checkmarks for GDL90 and GMU1

Master/Alternator on/off twice, pulled and pushed circuit breaker. No joy. Hoping it is loose connector, bent pins rather than the unit actually failing. My A&P will look at it in the morning (had a deadline project today).

Anyone have run into these before?

Robert

[aggiepilot04]

I had similar (and sporadic) symptoms following my GTX 345 install (see here: 

).  I believe that in my case, someone had leaned on the AHRS connections during the GTX345 install...which pulled the individual pins out  of the harness slightly.  After re-seating, I have not seen any issues.  In flight, I was able to resolve the problem by pulling and resetting the GPS1 and GPS2 breakers...but I'm sure it depends on which pins aren't making a good connection.

[Robert C.]

Yuck, reseated the pins and still no joy. Off to the avionics shop

[philiplane]

there is a 24 month calibration requirement for the magnetometer. Start there first.

[Robert C.]

7 hours ago, philiplane said:

there is a 24 month calibration requirement for the magnetometer. Start there first.

Interesting, I did not know that. I'll check that that has been happening.

[Robert C.]

For future reference:

The GMU44 had conked out on me. Shop replaced it and all is well. However, Mooneys have a slightly different bootblock and software setup than other G1000 installations, so the shop (unaware of the related SB) tried to install the GMU44 with what they had and "bricked" it. They sent out for another one and did it right, the 2nd time around. They're good people and were duly embarrassed. 

All's well that ends well

[LANCECASPER]

10 hours ago, Robert C. said:

For future reference:

The GMU44 had conked out on me. Shop replaced it and all is well. However, Mooneys have a slightly different bootblock and software setup than other G1000 installations, so the shop (unaware of the related SB) tried to install the GMU44 with what they had and "bricked" it. They sent out for another one and did it right, the 2nd time around. They're good people and were duly embarrassed. 

All's well that ends well

How much was it to replace the GMU44?

[Robert C.]

$600 for the GMU44 and $375 for the troubleshooting and installation labor plus $18.50 shipping. Total $993.50

[Mark W]

I recently had a similar but slightly different experience that I’ll summarize below in hopes of saving someone time and money troubleshooting.  

Airplane:  2005 Ovation GX with WAAS and GFC 700

issues:

1). Sporadic failure of traffic and WX-500 only during flight (never on the ground).  The problem started after upgrading my GX-1000 software to the latest version in March, 2018.  The prior software version was from about 2008.  I thought that the problem might be sporadic loss of heading information, which will cause the traffic and WX-500 to fail.  The Heading indicator requires a loss of information for about 2 min. so I would not see the problem there unless it persisted.  My avionics guy confirmed that he has seen this problem before and been told by Garmin that it is because the sampling rate of the newer software revision is too high for the old GMU 44.  The newer GMU 44s have a higher refresh rate and can keep up with the software.  We replaced the GMU 44 and the problem was solved (after he bricked it the first time).

2). After my last annual, I found that turning on my NAV lights caused my heading indicator to fail about 2 min and 20s later.  This was highly reproducible and happened only in the air.  The problem turns out to be related to the right trailing edge NAV light.  I had the light repaired at annual, including some wiring repairs, and this initiated the problem.  The ground point is a rib near the right wingtip.  When the right trailing edge NAV light comes on, the magnetometer interference test indicates over 28 Gauss versus about 0.45 Gauss with no NAV lights on.  Mooney told my avionics guy that the ground must be relocated to the fuselage using shielded wire.  For now, the rear NAV light has been removed and the problem is gone.  Relocating the ground is much harder than it sounds because the original ground is almost inaccessible without wingtip removal.

Mark

 

 

Edited October 9, 2018 by Mark W
Clarify wording and fix typos

[LANCECASPER]

2 minutes ago, Mark W said:

I recently had a similar but slightly different experience that I’ll summarize below in hopes of saving someone time and money troubleshooting.  

Airplane:  2005 Ovation GX with WAAS and GFC 700

issues:

1). Sporadic failure of traffic and WX-500 only during flight (never on the ground).  The problem started after upgrading my GX-1000 software to the latest version in March, 2018.  The prior software version was from about 1998.  I thought that the problem might be sporadic loss of heading information, which will cause the traffic and WX-500 to fail.  The Heading indicator requires a loss of information for about 2 min. so I would not see the problem there.  My avionics guy confirmed that he has seen this problem before and been told by Garmin that it is because the sampling rate of the newer software revision is too high for the old GMU 44.  The newer GM44s have a higher refresh rate and can keep up with the software.  We replaced the GMU44 and the problem was solved (after he bricked it the first time).

2). After my last annual, I found that turning on my NAV lights caused my headphones NT indicator to fail about 2 min and 20s later.  This was highly reproducible and happened only in the air.  The problem turns out to be related to the trailing edge NAV light.  I had the light repaired at annual, including some wiring repairs, and this initiated the problem.  The ground point is a rib near the wingtip.  When the rear NAV light comes on, the magnetometer interference test indicates over 28 Gauss versus about 0.45 Gauss with no NAV lights on.  Mooney told my avionics guy that the ground must be relocated to the fuselage using shielded wire.  For now, the rear NAV light has been removed and the problem is gone.  Relocating the ground is much harder than it sounds because the original ground is almost inaccessible without wingtip removal.

Mark

 

 

The G1000 wasn't introduced until late 2004, so the software couldn't have been from 1998. The WAAS came out around 2008 or so, so that may have been the last software update.

[Mark W]

You are correct.  I meant to say that the previous software was from 2008, not 1998.  Thanks for the catch.

[Robert C.]

Thanks Mark, that's a very helpful addendum to this post.

Robert

[Mark W]

You’re welcome.  Please note that I clarified the wording and fixed a couple of typographical errors, particularly in part b.

[carusoam]

Great detail Mark.

Thats going to be helpful to somebody.

Best regards,

-a-