Troubleshooting
GNS 480 (CNX80) Installation Manual560-0982-01 Rev A
4-1
4 T
ROUBLESHOOTING
This section provides information to assist troubleshooting if problems occur after completing the
installation. Use Table 4-1 to assist in troubleshooting. Devices connected to the GNS 480, such as an
SL30, SL70 or MX20 can be useful for determining whether the GNS 480 is functioning properly or if
there are problems with the installation.
4.1 T
ROUBLESHOOTING
P
ROCEDURE
Table 4-1. Troubleshooting Guide
Problem Possible
Cause
Solution
The GNS 480 does not
power on.
•
The unit is not getting power to the
main connector P1.
•
Make sure power is connected to the
main 37-pin connector P1-1 and 16 and
ground to P1-2 and 20. Check circuit,
breakers and main avionics switch.
The GNS 480 does not
compute a position.
•
Not receiving signals, or incorrect
seed position, time, and date.
•
Make sure a correct position and
time/date have been entered. Check the
GPS antenna connections. Make sure the
aircraft is clear of hangers, buildings,
trees, etc.
GPS signal levels drop
when avionics are
turned on.
•
Noise interference from other
avionics.
•
Turn all avionics off, then turn on each
piece one at a time to isolate the source
of the interference. Route GPS cable and
locate GPS antenna away from sources
of interference.
The GPS signal levels
are very low.
•
Improper antenna installation or
coax routing.
•
Antenna shaded from satellites.
•
RF interference at 1575.42 MHz
from VHF com.
•
Check GPS antenna installation,
connections, and cable routing. The GPS
antenna must be mounted on the top of
the aircraft.
•
Make sure the aircraft is clear of
hangers, buildings, trees, etc.
•
Move GPS antenna further from the com
antenna. Add a 1575.42 MHz notch
filter in com coax. Fix or replace the
com. Disconnect the ELT antenna coax
to check for possible re-radiation.
Unable to control Com
using
COM
bezel
key.
•
No power to the com.
•
The input voltage is too low.
•
Make sure power is connected to the
com 15-pin connector P4-1 and ground
to P4-9.
•
Increase input supply voltage to > 10
volts DC.
The GNS 480 does not
transmit.
•
The PTT input is not being pulled
low.
•
No power to the com.
•
The input voltage is too low.
•
Check that the PTT (mic key) input is
pulled low for transmit.
•
Make sure power input is connected to
the com 15-pin connector P4-1 and
ground to P4-9.
•
Increase input supply voltage to > 10
volts DC.
Summary of Contents for GNS 480
Page 1: ...GNS 480 CNX80 Color GPS Nav Com Installation Manual September 2004 560 0982 01 Rev A...
Page 10: ...Table of Contents viii 560 0982 01 Rev A GNS 480 CNX80 Installation Manual NOTES...
Page 30: ...General Information 1 20 560 0982 01 Rev A GNS 480 CNX80 Installation Manual NOTES...
Page 126: ...Periodic Maintenance 6 2 560 0982 01 Rev A GNS 480 CNX80 Installation Manual NOTES...
Page 150: ...Appendix D Interconnect Diagrams D 2 560 0982 01 Rev A GNS 480 CNX80 Installation Manual NOTES...
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