Troubleshooting; Troubleshootingp - Garmin GNS 480 Installation Manual

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
Problem
• The unit is not getting power to the
The GNS 480 does not
power on.
• Not receiving signals, or incorrect
The GNS 480 does not
compute a position.
• Noise interference from other
GPS signal levels drop
when avionics are
turned on.
• Improper antenna installation or
The GPS signal levels
are very low.
• Antenna shaded from satellites.
• RF interference at 1575.42 MHz
• No power to the com.
Unable to control Com
COM
using bezel
key.
• The input voltage is too low.
• The PTT input is not being pulled
The GNS 480 does not
transmit.
• No power to the com.
• The input voltage is too low.
GNS 480 (CNX80) Installation Manual560-0982-01 Rev A
P
ROCEDURE
Table 4-1. Troubleshooting Guide
Possible Cause
main connector P1.
seed position, time, and date.
avionics.
coax routing.
from VHF com.
low.
Solution
•
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.
•
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.
•
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.
•
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.
•
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.
•
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.

Troubleshooting

4-1