Update:
After checking the second solenoid located in the back of the converter panel enclosure, I found the left (red cable) is connected to the converter breaker panel (see photo). When connected to shore power this wire is hot, but when disconnected from shore power and in the current "non-functional battery to coach" state, there is no power to the red cable and therefore its not powering the converter breaker panel. While connected to shore power I also tried toggling the momentary "Use/Store" house power supply switch, to no avail. (PS: Factory installed solenoid, not me - I'm more picky)
The right (black cable) attached to the solenoid is incoming from the house battery compartment and the under-coach solenoid. There is power to this lug whether connected to shore power or not (makes sense).
While squeezed into this converter panel compartment I managed to ground a wrench and create a spark (unplugged from shore power
) and then noticed there was no power to the right side cable incoming from the battery compartment. I found the 50amp fuse tripped. Actually this was a blessing because now I know it works and I was able to reset it.
That said, it seems like the only component remaining other than the ATS is this little isolator relay delay (see photo), which I have no clue as to its function and I've not replaced it. Its also located under the coach and adjacent to the #1 solenoid (Trombetta) with two wires connected to the solenoid and one leading off to a harness that terminates to the "Use/Store" momentary switch. So if there is no "output" from this sealed box over to the Use/Store switch then no signal can be sent to turn on/off the battery power supply. Thoughts?
But I'm starting to think that lwmcguire might have the final thought in that its the ATS.