Well...update time. I wish it was as easy as a switch or corrosion.
I found a service manual (online) and found the issue listed in the "Troubleshooting" section. I followed the corrective action steps and verified both switches (and wiring) are functioning as they should. The last instruction listed is "Replace the controller assembly"
Basically the problem lies somewhere in the control board. After finding the Onan part number in the manual (another online manual) we learn that the control board is "not a field serviceable part." The entire assembly...including the inverter must be purchased. (cost in excess of 2500.00)
Additionally, we also need to drop the unit out of the motorhome to allow full access.
Needless to say I am pretty upset/disappointed that we have once gain fallen victim and have yet another example of the "computer controlled throw-away society" in which we now live. I am grateful that I have the ability to do some of the work myself...although I will have to work on garnering enough motivation to do so.
I plan to contact some of the repair companies (flight services ect) and see if it is possible to ease the hit.
Can anyone offer other suggestions for control board repair companies? Anyone willing to share there experiences with said repair companies? Should I bite the bullet and buy the "genuine Onan" assembly?