Gad 42 Interface Check; Lighting Bus Interface Check; Figure 6-43. Gad 42 Configuration Page; Figure 6-44. Lighting Configuration Page - Garmin GTN 635 Installation Manual

6.10.8 GAD 42 Interface Check

This check verifies that the GTN is interfaced with the GAD 42.
1. Access the GAD 42 Configuration page, as shown in
Figure 6-43, by touching the ‗GAD 42' key on the
External Systems page.
2. Verify that Status is ACTIVE.
3. Change any of the options to a different number.
4. Verify that after changing one of the options the
STATUS field changes to SENDING then changes back
to ACTIVE. If the entry reverts to the previous number when ACTIVE is displayed, then refer to
the latest revision of the GAD 42 Installation Manual (P/N 190-00159-00).

6.10.9 Lighting Bus Interface Check

When 14 VDC or 28 VDC lighting buses are connected to the GTN, connection of the
aircraft lighting bus to the incorrect input pins can cause damage to the GTN. Always start
this test with the dimming bus at the lowest setting, and slowly increase the brightness. If it
is noticed that the LIGHTING level displayed on the GTN does not increase as the lighting
is increased in brightness, verify that the wiring is correct before proceeding.
The display and key backlighting on the GTN can track an external lighting/dimmer bus input and use it
to vary the display and key backlight levels accordingly. This check verifies that the interface is
connected correctly.
1. Access the Lighting Configuration page, as shown in
Figure 6-44, by touching the ‗Lighting' key on the GTN
Setup page.
2. Touch the Source key to change the source to Lighting
Bus 1 or 2.
3. Touch the Minimum Level key to set the lighting bus to
its minimum setting of 0.14%.
4. Slowly vary the lighting bus level that is connected to
the GTN. Verify that the Source Input Level value
displayed on the configuration screen tracks the lighting bus setting. Continue to maximum
brightness and verify proper operation.
GTN 625/635/650 TSO Installation Manual
190-01004-02

Figure 6-43. GAD 42 Configuration Page

CAUTION

Figure 6-44. Lighting Configuration Page

Page 6-35
Rev. C