190-02081-03
GFC 600H HFCS Part 27 STC Maintenance Manual
Rev. 3
Page 5-10
5.3 GRS 79H or GSU 75H ADAHRS and GMU 44( ) Magnetometer
For troubleshooting any AHRS/ADC faults in installations with a Garmin G500H system (GDU 620 or
TXi), see prior installation data approval for the specific corrective actions.
Table 5-5 describes possible symptoms associated with the Garmin Standalone AHRS/ADC Installation
Tool and provides corresponding actions for troubleshooting.
Table 5-5 General Troubleshoot Guide for AHRS/ADC Install Tool
The following error messages can alert the installer in the AHRS/ADC Install Tool during configuration
and calibration of the GRS 79H or GSU 75H and GMU 44( ) units.
Table 5-6 ADC Field Calibration Troubleshooting
Symptom
Recommended Action
Post-install procedures will
not complete.
• Ensure the Communication Status for GPS, Air Data and
Magnetometer are all
green checked
.
• Ensure the aircraft is in an area free of magnetic interference and
away from ferrous metal objects.
• Ensure that equipment, wiring or ferrous/magnetic material are not
installed too close to the GMU 44( ).
• Ensure that an electronic device has
NOT
become grounded
through the aircraft structure instead of the proper ground wire,
especially if the ground return path through the aircraft structure
passes within 10.0 feet of the GMU 44( ).
• Ensure the GPS antenna has an unobstructed clear view of the sky
and the navigator has acquired a valid signal.
• Ensure wiring is correct.
Red ‘X’ next to data source in
Communication Status and/or
over data in AHRS Data
windows under the AHRS
Menu.
OR
Red ‘X’ over data in Air Data
or Pressure Data under the
ADC Menu.
• Ensure the aircraft is in an area free of magnetic interference and
away from ferrous metal objects.
• Ensure the GPS antenna has an unobstructed clear view of the sky
and the navigator has acquired a valid signal.
• Ensure the pitot-static system is free of debris and obstructions.
• Ensure the GMC 605H, GFS 83, GRS 79H or GSU 75H, and
GMU 44 connectors are securely mated to the units.
• Ensure wiring is correct.
• If problems persist, contact Garmin.
Annunciated Fault
Possible Cause
Corrective Action
Measured altitudes
are out of range
Altitudes measured during the
calibration are not within
acceptable range to compute
correction coefficient.
• Ensure there are no leaks between the
pitot-static test set and the GSU 75H.
• Repeat the calibration.