Garmin GPS 400W,GNC 420W User Manual (English)

Other manuals for Garmin GPS 400W,GNC 420W

Questions and Answers:

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ruben82Aug 27, 2025
How to improve low GPS signal levels on my Garmin?
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  Dorothy BarnesAug 27, 2025
  Very low GPS signal levels can be caused by a few things. First, check the GPS antenna installation, connections, and cable routing, ensuring the antenna is mounted on top of the aircraft. Also, make sure the aircraft is clear of hangars, buildings, trees, etc., which could be shading the antenna from satellites. Finally, RF interference at 1575.42 MHz from VHF COM can be a factor; try moving the GPS antenna further from the COM antenna, adding a 1575.42 MHz notch filter in the COM coax, fixing or replacing the COM, or disconnecting the ELT antenna coax to check for possible re-radiation.
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kvanceAug 27, 2025
What to do if my Garmin 400W Series GPS unit does not transmit?
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  Alexander WalkerAug 27, 2025
  If the 400W Series unit doesn't transmit, it could be because the PTT input isn't being pulled low; check that the PTT (mic key) input is pulled low for transmit. Another reason could be no transmit power to the COM; ensure the power input is connected to the COM 25-pin connector P4002 11 and 12 and ground to P4002 21 and 22. The input voltage might also be too low; increase the input supply voltage to >12 VDC (>24VDC for 420 AW and 430AW models).
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Randy RandallAug 27, 2025
Why does my Garmin GPS keep 'searching the sky'?
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  Jay HutchinsonAug 27, 2025
  The unit is actively searching for GPS satellites. Allow up to 20 minutes for the unit to complete its cycle or until your current position is located.
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John LewisAug 28, 2025
What to do if Garmin GPS signal levels drop when avionics are turned on?
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  Patrick WilsonAug 28, 2025
  If the GPS signal levels drop when you turn on your avionics, it's likely due to noise interference from other avionics. To resolve this, turn off all avionics and then turn them on one at a time to identify the source of the interference. Also, try routing the GPS cable and positioning the GPS antenna away from potential interference sources.
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Spencer CookAug 28, 2025
What to do if Garmin GPS signal levels are very low?
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  matthewrodriguezAug 28, 2025
  Low GPS signal levels can stem from several factors: * Improper antenna installation or coax routing: Ensure the GPS antenna is correctly installed, with proper connections and cable routing. The antenna should be mounted on top of the aircraft. * Antenna shaded from satellites: Make sure the aircraft is in an open area, away from hangars, buildings, and trees. * RF interference: If there's RF interference at 1575.42 MHz from VHF COM, try moving the GPS antenna further from the COM antenna, adding a 1575.42 MHz notch filter in the COM coax, fixing or replacing the COM, or disconnecting the ELT antenna coax to check for possible re-radiation.
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Gregory HendersonAug 28, 2025
Why Garmin 400W Series GPS unit does not compute a position?
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  wyatterinAug 29, 2025
  If your 400W Series unit isn't computing a position, there could be a few reasons: * Not receiving signals: Check the GPS antenna connections and ensure the aircraft is clear of obstructions like hangars, buildings, and trees. * Unit cycling: Wait 20 minutes for the unit to complete its cycle.
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Ryan ToddAug 25, 2025
How to fix Garmin 400W Series GPS unit that does not power on?
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  Nathan RichardsonAug 25, 2025
  If your 400W Series unit isn't powering on, the issue might be that the unit isn't getting power to the main connector P4001. Ensure power is connected to the main 78-pin connector P4001, pins 19 and 20, and ground to P4001, pins 77 and 78. Check the circuit breakers and main avionics switch as well.
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Deborah SmithAug 29, 2025
How to resolve Garmin airport database integrity error?
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  Lindsay Mason DVMAug 29, 2025
  If your 400W Series unit displays an “ database integrity error” message, it means the unit has detected a problem with a database on the NavData card, rendering the data unusable. Try reloading the information onto the card. If the problem persists, replace the card.
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Dr. Jonathan TaylorAug 30, 2025
How to fix Garmin RS-232 device that is not communicating with the 400W Series unit?
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  Austin MarshallAug 30, 2025
  If an RS-232 device isn't communicating with the 400W Series unit, there are several things to check: * 400W Series unit RS-232 port configuration: Check the RS-232 port setting for the port that the device is connected to. * Remote device setup: Verify the configuration of the other device. * Device compatibility and connection: Verify the 400W Series unit RX is connected to the remote device TX, and the 400W Series unit TX is connected to the remote device Rx. * Multiple TX lines: Verify that there is only one TX source per RX port. * Wiring: Check wiring.
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beardlouisAug 30, 2025
How to fix Garmin ARINC 429 device that is not receiving data from the 400W Series unit?
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  Marcus ThompsonAug 30, 2025
  If an ARINC 429 device isn't receiving data from the 400W Series unit, check the following: * 400W Series unit ARINC 429 output configuration: Check the ARINC 429 output port setting for the port that the device is connected to. * ARINC 429 input port speed: Check the ARINC 429 input port speed setting for the port that the device is connected to and verify that the speed is correct for that device. * Wiring: Check wiring.

Garmin GPS 400W,GNC 420W Specifications

General

Display	5.0" diagonal, 256 colors TFT
Resolution	320 x 234 pixels
WAAS	Yes
Operating Temperature	-20°C to +55°C
Update Rate	1 Hz
Database	Jeppesen
COM Frequency Range	118.000 to 136.975 MHz
COM Channel Spacing	25 kHz
NAV Frequency Range	108.00 - 117.95 MHz