190-01007-01
GTN 725/750 Maintenance Manual
Rev. 5
Page 4-8
Table 4-6 COM Messages (GTN 750 Only)
Table 4-7 TAWS Messages
Alert Text
Possible Cause
Corrective Action
COM RADIO -
COM overtemp or
undervoltage.
Reducing
transmitter power.
The COM board is reporting
an overtemp or undervoltage
condition.
• Check bezel and fan for freedom from
obstruction and ensure the fan is functioning
properly.
• Check for adequate airflow around the GTN.
• Check aircraft input power. Refer to appendix
A.3 for pinout information.
a) If voltage with reference to aircraft ground
is less than 11 VDC, the cause is an
undervoltage condition. Check aircraft
power.
b) If voltage with reference to ground is
greater than 11 VDC, the cause is an
overtemperature condition. Troubleshoot
the fan.
• If the message persists, replace the GTN.
Refer to section 5.1 for details.
COM RADIO -
COM radio may be
inoperative.
The COM radio has detected
an internal failure in its COM
radio and may not be
receiving power.
• Cycle the GTN COM Circuit Breaker.
• Check power and ground wiring to the COM
board. Refer to appendix A for pinout
information.
• Replace the GTN. Refer to section 5.1 for
details.
COM RADIO -
COM radio needs
service.
A failure has been detected
in the COM transceiver. The
transceiver may still be
usable.
• This message may appear after operations in
configuration mode or power cycling the GPS/
NAV separately from the COM. Cycle power to
the entire GTN (both GPS/NAV and COM
circuit breakers) and see if the message has
cleared.
• If the message persists, replace the GTN.
Refer to section 5.1 for details.
Alert Text
Possible Cause
Corrective Action
CONFIGURATION
- Terrain/TAWS
configuration is
invalid. GTN needs
service.
The TAWS configuration is
invalid due to a loss or
corrupt registry.
• The TAWS/terrain configuration settings must
be reselected. Reselect the TAWS or terrain
selection and cycle power to the GTN.
• If the problem persists, contact Garmin
Technical support.
