Thanks Dan & John.
I believe you guys may have nailed it.
With the starter key engaged I get 12v across the master relay.
Disengaged, I was getting 2v. Someone suggested it may be "ghost" voltage, but it may be enough to deactivate my avionics bus.
Dan, I'll try your setup with the master relay diode to ground & see if that resolves the problem.
Danny "RoadRunner" Landry
Morphed RV7(formally 7A), N20DL, PnP Pilot
2019 Donation Paid