OBS mode unavailable

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   IFD 540  IFD 440  GI275 x 2   GFC500.I also kept a backup CDI and had the shop wire that for VOR/ILS approaches.
My mode switch works correctly from GPS to VLOC on both 540 and 440.
The ILS and VOR work correctly on the backup CDI.
Pushing the OBS button on either the 540 or the 440 does nothing.
My autopilot won''t track a VOR.
I believe the shop told me I could have either the 275 or the backup CDI
but not both.  Is the wiring this way preventing OBS mode on the Avidynes?
And also preventing the GFC 500 from tracking the VOR?
Bob

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rpostmo Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 20 Jul 2015 Location: North Dakota Status: Offline Points: 164	Post Options Post Reply Quote rpostmo Report Post Thanks(0) Quote Reply Topic: OBS mode unavailable Posted: 04 Jun 2023 at 2:13pm
	IFD 540 IFD 440 GI275 x 2 GFC500. I also kept a backup CDI and had the shop wire that for VOR/ILS approaches. My mode switch works correctly from GPS to VLOC on both 540 and 440. The ILS and VOR work correctly on the backup CDI. Pushing the OBS button on either the 540 or the 440 does nothing. My autopilot won''t track a VOR. I believe the shop told me I could have either the 275 or the backup CDI but not both. Is the wiring this way preventing OBS mode on the Avidynes? And also preventing the GFC 500 from tracking the VOR? Bob

rpostmo Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 20 Jul 2015 Location: North Dakota Status: Offline Points: 164	Post Options Post Reply Quote rpostmo Report Post Thanks(0) Quote Reply Posted: 12 Jun 2023 at 12:35pm
	Operator error! CRS button on the 275 must be pressed for OBS to work. It defaults to HDG whenever a change is made in course or the HSI indicator is changed and must be pressed again when OBS function is desired. The OBS mode will persist appropriately if other nav changes are not made. Both the GI275 and the backup CDI will show 3 axis course on the ILS simultaneously, or like I prefer, the ILS shows on the CDI and I leave magenta needles on the 275. The GFC500 tracks all of these correctly: GPS, VOR, Localizer, Glideslope, LPV glidepath. All in all an amazing combination once all the intricacies are realized (and practiced). Bob