Newbie , '89 Dodge Xplorer, no manual, help!

I think the battery in the Xplorer is mounted in the floor under the entry step. There should be a big cable going from there to the 12 volt distribution box under the closet. You should see if you're getting 12 volts at the distribution panel. It's easily checked with a VOM.

I don't think the Xplorer has a 12 volt house disconnect switch

karl