Shore line not charging battery

[provideo]

Hello. I have a 2006 GS 5231 BT Cruiser with a battery problem. The cabin battery slowly drains when the shore line is plugged in. All 110AC outlets work properly but the battery is not charging. If I start the truck engine it switches over properly and charges as expected. If I start the onboard generator it switches over properly and charges as expected. It is not switching over when the shore line is in use. Since the 110AC from the generator switches over properly I would say the "converter" is working. So why is the shore line not switching? Has anyone seen this problem before?

Also, where on this earth can I find a wiring diagram for my 2006 GS 5231 ? Surely someone out there has one. Any help would be greatly appreciated.
Thanks,
Mike from Oklahoma