Garmin GPS 400W Installation Manual

Also see for GNC 420AW: Maintenance manual Pilot's guide addendum Quick reference guide Pilot's Guide & Reference Pilot's Guide & Reference

Contents

Garmin GPS 400W Installation Manual Manual pdf 113 page image

400W Series Installation Manual Page 6-1190-00356-02 Rev. A6. TROUBLESHOOTINGThis section provides information to assist troubleshooting if problems occur after completing theinstallation. Devices connected to the 400W Series unit can be useful for determining whether the 400WSeries unit is functioning properly or if there are problems with the installation.6.1 Troubleshooting ProcedureTable 6-1. Troubleshooting GuideProblem Possible Cause SolutionThe 400W Series unitdoes not power on.• The unit is not getting power tothe main connector P4001.• Make sure power is connected to themain 78-pin connector P4001, pins 19and 20 and ground to P4001, pins 77and 78. Check circuit breakers andmain avionics switch.• Check the GPS antenna connections.Make sure the aircraft is clear ofhangars, buildings, trees, etc.The 400W Series unitdoes not compute aposition.• Not receiving signals.• Wait 20 minutes for unit to completecycle.GPS signal levelsdrop when avionicsare turned on.• Noise interference from otheravionics.• Turn all avionics off, then turn on eachpiece one at a time to isolate the sourceof the interference. Route GPS cableand locate GPS antenna away fromsources of interference.• Improper antenna installation orcoax routing.• Check GPS antenna installation,connections, and cable routing. TheGPS antenna must be mounted on thetop of the aircraft.• Antenna shaded from satellites. • Make sure the aircraft is clear ofhangars, buildings, trees, etc.The GPS signal levelsare very low.• RF interference at 1575.42 MHzfrom VHF COM.• Move GPS antenna further from theCOM antenna. Add a 1575.42 MHznotch filter in COM coax. Fix orreplace the COM. Disconnect the ELTantenna coax to check for possible re-radiation.• The PTT input is not beingpulled low.• Check that the PTT (mic key) input ispulled low for transmit.• No transmit power to the COM. • Make sure power input is connected tothe COM 25-pin connector P4002 11and 12 and ground to P4002 21 and 22The 400W Series unitdoes not transmit.• The input voltage is too low. • Increase input supply voltage to >12VDC. (>24VDC for 420 AW and430AW models)