Instruction Manual

400W Series P/N 190-00356-65 Rev. D
Instructions for Continued Airworthiness Page 6 of 12
5. Inspect electrical bonding components. Perform bonding check, if due (see Section 2.5.4).
2.5.1 Cleaning the Front Panel
The front bezel, keypad, and display can be cleaned with a soft cotton cloth dampened with clean water.
DO NOT use any chemical-cleaning agents. Care should be taken to avoid scratching the surface of the
display.
2.5.2 Display Backlight
The display backlight lamp is rated by the manufacturer as having a usable life of 20,000 hours. This life
may be more or less than the rated time depending on the operating conditions of the 400W series unit.
Over time, the backlight lamp may dim and the display may not perform as well in direct sunlight
conditions. The user must determine by observation when the display brightness is not suitable for its
intended use. Contact the Garmin factory repair station when the backlight lamp requires service.
2.5.3 Battery Replacement
The 400W series has an internal keep-alive battery that will last about 10 years. The battery is used for
GPS system information. Regular planned replacement is not necessary. The 400W series will display a
‘low battery’ message when replacement is required. Once the low battery message is displayed, the
battery should be replaced within 1 to 2 months.
If the battery is not replaced and becomes totally discharged, the 400W series unit will remain fully
operational, but the GPS signal acquisition time may be increased. This acquisition time can be reduced
by entering a new seed position each time the unit is powered on. There is no loss of function or
accuracy of the 400W series unit with a dead battery.
The battery must be replaced by the Garmin factory repair station or factory authorized repair station.
2.5.4 Bonding Check (IFR-certified aircraft only)
Every 2000 flight hours or ten (10) years, whichever is first, perform an electrical bonding check on the
GNS 400W Series Unit and if installed, the Flight Stream 210. If a bonding check was not done during
the initial installation, it must be done to support electromagnetic interference and lightning compliance.
2.5.4.1 GNS 400W Series Unit in Metallic or Tube/Fabric Aircraft
Perform an electrical bonding check as follows:
1. Remove the 400W unit from the mounting rack.
2. Remove the backplate assembly from the rack.
3. Measure the resistance between the mounting rack and nearby exposed portion of aircraft
metallic structure and verify it is less than 10 milliohms.
In the event of bonding test failure, remove the 400W rack and clean the attachment points with
a bonding brush at both the 400W rack and the aircraft and reattach the rack to the rails in the
panel. Verify the resistance between the mounting rack and nearby exposed portion of aircraft
metallic structure is less than 2.5 milliohms.
4. Reinstall the backplate assembly and reinstall the 400W in the mounting rack.