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GNS 400W Series Maintenance Manual
Page 4-3
190-00356-05
Rev. A
Table 4-1. Fault Messages and Recommended Actions (continued)
Check unit cooling
The unit has detected
excessive display
backlighting temperature. The
backlighting has been
automatically dimmed to
reduce the temperature.
Check for adequate
ventilation or check cooling
airflow.
Return the unit to Garmin for
repair.
COMM has failed
The unit has detected a
failure in the communications
transceiver.
Replace the comm board.
Return the unit for service.
COMM is not responding
Internal system-to-system
communication between the
main processor and the com
radio has failed. Operational
status of the com radio is
unknown.
Replace the comm board.
Return the unit for service.
COMM needs service
N/A
Replace the comm board.
COMM push-to-talk key stuck The external push-to-talk
(PTT) switch is stuck in the
enabled (or “pressed”) state.
Press the PTT switch again to
cycle its operation, if the
message persists, return the
unit to Garmin for repair.
COMM remote transfer key is
stuck
The remote COMM transfer
switch is stuck in the enabled
(or “pressed”) state.
Press the switch again to
cycle operation.
Verify that microphone key
line is not stuck on before
replacing comm board.
Replace the comm board.
COMM mic key stuck
N/A
Verify that remote transfer
key line is not stuck before
replacing comm board.
Replace the comm board.
COMM transmitter power has
been reduced
N/A
Check for excessive unit
temperature.
Verify that power input to J2-
11 and 12 has not dropped
below 26 V (for a 28 volt unit)
or 12 V (for a 14 volt unit)
when transmitting before
replacing the comm board.
Replace the comm board.
