First, let me be clear....I am not familiar with your Progressive Dynamics fuse panel / power distribution panel.
But......
It appears to have a huge relay or power transfer switch integrated inside it, the devise with the blue circle. With the panel open as you have pictured, plug your RV into 110V and see if it clicks into one position or another. Your hand written voltage readings indicate otherwise, but it just might involve 110V under certain conditions. Who knows what the RV industry practiced back in 1979. Take voltage readings on all the terminals under these 4 different power-support conditions.
- when plugged into shore power
- with the generator running
- with the main engine running
- with nothing running.
Unrelated to that.......
If your Progressive Dynamics power distribution panel does not have a big transformer, than you must have a separate 110V to 12V power converter located somewhere else inside the motor home, maybe behind that Progressive Dynamics power distribution panel.
Everything I am saying here is subject to great scrutiny.
