"My new to me Vision, did not charge the house batteries from the nator."
That is a great workaround. On my last mh before I added the Trik-l-start charger I installed a standard automotive tail light bulb in line between the tow battery systems. It was used only when sitting. A simple alligator clip on each end. This kept charging current very low and when there was enough current it would glow. Once it quit glowing for many hours it was charged. Crude but fun and effective.
Many rv's are not set up to charge the engine batteries when on shorline. I believe Winnebago is now installing the trik-l-start as standard equipment. With the addition of a moderate sized solar panel my batteries were always up.
This said, you probably have a blown fuse that drives the solenoid. It would bug me to not find the cause.