It is fixed
Thanks for the ideas & suggestions
Dad had to take it to the shop anyway as he couldn't get it going
The Onan service center was able to get him in quickly & worked over to fix it
It isn't mounted on a slide, so that cost more
It turned out that water had gotten into the unit & ruined the main control board
Dad was surprised that we got good ideas so quickly. I told him that this board is one of the best thing about being a bus nut. The best is having a bus & a plan!