Troubleshooting On-Board The Aircraft - Garmin G300 Installation Manual

10.5 Troubleshooting On-board the Aircraft

1. Review the airframe logbook to verify if any G300 or other avionics or electrical
maintenance had been performed recently that may have contributed to the failure.
2. Check for loose wire terminals on the circuit breaker connections on the power wire(s)
causing intermittent power connections. Also, check for intermittent circuit breakers.
3. Have ground power put on the aircraft.
4. Turn on G300 and record the system software level on the GDU start up page.
5. After the system is initialized, note any Red-X's on the displays, ALERT messages and Red-
X's on the GDU.
If the failure cannot be verified, proceed to the following physical inspection.
1. Turn off G300 and remove the interior panels to gain access to the GSU 73. Inspect
the physical installation of the GSU 73.
2. Check that the connectors are fully seated, and that the jack screw connectors are fully
tightened on both sides of the GSU 73 connector.
3. Check for a loose wire harness that is able to move around during flight. This condition may
cause the wire to pull on or vibrate the connector making intermittent connections.
4. Ensure that the GSU 73 is mounted securely. If any doubt exists, use a screwdriver to check
the tightness of the four mounting screws.
5. Look in the vicinity of the GSU 73 for any heavy objects that may not be fastened tight to the
structure that could induce GSU 73 vibration.
6. Look for evidence of water or fluid contamination in the area around the GSU 73.
7. Unplug the GSU 73 connector and check for bent pins.
8. Inspect the wire harness clamp on the rear of the connector to verify that it is not too tight and
smashing/shorting the wires. If the wire clamp is installed upside down, it has sharp edges
that can cut into the wires. Also verify the presence of protective wire wrap between the
wires and the clamp.
If the condition is not resolved by following the preceding instructions, contact Garmin Product Support
for additional assistance. A Garmin Field Service Engineer may ask the technician to download the fault
logs to a PC (via the USB port on the GSU 73) and email the logs back to Garmin to help determine if the
problem is in the GSU 73 or in the aircraft.
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Revision A
G300 Installation Manual –Troubleshooting
190-00921-01