Just went through this myself. The Generator in my coach starts off the chassis battery. The 2 house batteries in my coach are connected positive to positive, negative to negative to ground. The auxiliary solenoid cable needs to be connected to positive. I orignally had it connected to negative and nothing inside worked. I actually paid a mobile mechanic to come out and he said everything was connected properly. So NOT! I followed my hunch, connected the batteries and aux solenoid the way I thought it should go and everything worked from that point on.
From this day forward make it your vow, Take "Someday I'll" and make it your Now!