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Troubleshooting
MESSAGE
COOLING FAN -
The cooling fan has
failed.
DISPLAY -
Display board needs
service.
FEATURE UNLOCK
FAILURE -
GLIDESLOPE -
Glideslope receiver
needs service.
GLIDESLOPE -
Glideslope receiver has
failed.
NO UNLOCK FILE -
NOTE
The GNC 255's system ID is required when downloading the frequency database.
See section 3.5.8 for details on the system ID.
5-4
DESCRIPTION
The GNC cooling fan is
powered, but it is not
turning at the desired
RPM.
The display board is
indicating that it needs
service.
The database on the USB
flash drive is corrupt or
the system ID in the
database does not match
the unit's system ID.
The glideslope board is
indicating that it needs
service. The glideslope
board may continue to
function.
The glideslope board is
not communicating
property with the system.
The USB flash drive is
missing the feature
unlock file for the
frequency database.
Garmin GNC 255A/255B Pilot's Guide
ACTION
Decrease cabin
temperature and increase
cabin airflow (especially
near the GNC) to prevent
damage to the unit.
Contact dealer for service.
Contact dealer for service.
Verify that the correct
system ID is entered into
flyGarmin.com when
downloading the database.
Contact Garmin Customer
Support if this message
persists.
Verify glideslope deviation
indications with another
source and crosscheck final
approach fix crossing
altitude. If another
glideslope source is not
available for verification, fly
a GPS based approach.
Contact dealer for service.
Fly an approach that does
not use the glideslope
receiver (VOR, LOC, GPS).
Contact dealer for service.
Verify the correct system ID
is entered on
flyGarmin.com and the
frequency database is
downloaded onto the USB
flash drive. Contact
Garmin Customer Support
if this message persists.
190-01182-01 Rev. E
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