Since I figure you guys have installed or built just about every manner of flying conveyance and experimented with all forms of flying machine, I'm hoping someone out there can give me some guidance on this little problem with my far less exciting than experimental Grumman AA1. I had Narco 122 (original 1970's unit) give up the ghost on me so I purchased a newer Narco 122 d/gps unit to replace it (supposedly a pin for pin swap that doesn't require any additional wiring). I put the unit in the same location and used the legacy connector and antenna wires and was able to get the VOR Morse code signal to come through, however when I went flying this morning the GS and Nav needles didn't actually indicate anything! Any ideas? I will say that I failed to connect the ground lug in the back of the unit (will remedy that this weekend). Would my failure to attach the grounding wire have any impact on the unit's function or am I looking at checking in with an avionics shop? Any advice would be appreciated.