Going from Run to Start cuts off non-essentials and the power to the solenoid normally. So there are switches of some sort responding to the key position. You try to start normally but the engine battery is too low.
You push MOM and try again using the key to Start. Non-essentials are still switched off same as usual, but this time power stays on to the solenoid (or there would be no power to the starter).
If the house battery power is just passed through to the engine side via solenoid, the brain that gets the power to run and switch off the non-essentials would not know the difference which battery bank is supplying the power. Seems to be the case.
But now for some reason the brain running the power to the solenoid can tell the difference?
Maybe the MOM by-passes the solenoid to parallel the house with the engine batt some other way, and it all acts the same as when on engine battery, but the solenoid being open in Start does not cut off the house battery power, because it by-passes the solenoid when in MOM??
I don't know. The schematic posted earlier was too complicated for me.
