Q. My GNS 430/GNC 420 display appears to "wash out" or becomes increasingly difficult to see during periods of extended operation and/or flight. Do I need to have my GNS 430/GNC 420 serviced?

As the operating temperature of a GNS 430/GNC 420 increases, or in cases of cold startups, you may want to fine tune the display contrast to your preference. High operating temperatures that require this adjustment typically are not damaging to the unit and in some instances can be related to the efficiency of airframe cooling that is provided from behind the installation position of the GNS 430/GNC 420. To adjust the display contrast setting in the GNS 430/GNC 420 use the following steps:

NOTE: Adjusting the "Auto Level" of the display contrast may negatively affect the display contrast at other operating temperatures. Keep track of the factory setting prior to making changes in case you want to return to this setting, which represents the best overall display characteristics over a wide temperature span. The unit is set at the factory to automatically compensate for changes to temperature and reverting to the "manual" mode will override this stored setting and require manual adjustment going forward. By adjusting the "Auto Level" the unit retains the ability to compensate over temperature fluctuations.

1. With the GNS 430/GNC 420 operating in normal mode, turn the large FMS knob to select the AUX page group.
2. Turn the small FMS knob to select the Setup 2 page (labeled at the top of the screen).
3. Press the small FMS knob to activate the cursor, and turn the small FMS knob to highlight "Display."
4. With "Display" highlighted, press the ENT (Enter) key.
5. Turn the large FMS knob to highlight the value under "LVL" for the Contrast line.
6. Now turn the small FMS knob counter-clockwise to reduce the contrast level or clockwise to increase the contrast level until reaching the desired level.
7. Once the contrast is set at the desired level, press the small FMS knob to exit this screen.
8. To exit the Setup 2 page, press the small FMS knob to clear any highlighted menu options, then turn the large FMS knob to select a desired page group. For help with navigating to additional pages or page groups, please refer to your GNS 430 series Pilot's Guide.