Received reply from Garmin on my issues. Worked some more and resolved all the issues.
Transponder fault - confirmed that it was most likely because I didn't enter the aircraft information yet. I may find a different problem when I do that, but for now it is working as expected.
Unable to select and configure some analog and digital inputs - there was a software bug that messed with some of the GAD 27 inputs so you could see ones you had configured, but not edit them. After I updated software that started working as I expected. The GEA 24 inputs seemed to have a similar problem even after the software update. Garmin explained how it really works so all is okay. There are two GEA 24 configuration tabs, GEA24 inputs and GEA24 discrete (digital) inputs. The GEA24 inputs tab shows all the analog inputs and 7 general purpose inputs. The GEA 24 discrete inputs tab also shows the 7 general purpose inputs. Before they are configured, they show up with a “-“ in the “type” column. You can see, select and configure them from either the inputs tab or the discrete tab. On the inputs tab, you can only configure them to be an analog type input. On the discrete tab, you can only configure them to be active high or active low. Once you configure them on one of the tabs, you can only edit them on the one tab (inputs or discrete). If you edit them and set the input type to “none” again you can select and edit them from either tab.
GAD 29 ARINC 429 not showing up on the main display, but LEDs flashing like the GAD 29 was communicating on the CAN bus and all was well. Garmin suggested sending it in for test/repair. I decided to do a little more testing and found out that if I left the power and CAN bus connector plugged in and disconnected the connector with the ARINC 429 bus signals the GAD 29 module showed up on the main display and had the latest software already installed. So I opened up the ARINC 429 bus signal connector and found I had put one of the pins in the wrong place. Why would that keep the system from working? Maybe because I had connected one ARINC 429 bus pin to a position that was marked as “reserved”. I had just put it in the wrong channel or swapped polarity I bet the GAD 29 would have shown up properly on the main display, but of course the ARINC 429 communications would have failed and I would have looked at the connector and found the problem easily.
Repaired the GAD 29 connector after completing the trouble shooting above. Replaced labels on the first blocks to match the way I had actually wired them. Updated the schematic to match the changes. Cleaned up wiring to the GAD 27 terminal block by reducing the length of some wires and rerouting. Cleaned up some other wire routing problems such as wires to the CO Detector and tied more wire bundles.
Reviewed shopping carts and notes to complete an Aircraft Spruce order.
The instrument panel wiring is basically complete and working although I need to move everything to the fuselage and connect up other components instead of just simulating them one at a time.