Hey Joe, I had the exact same thing happen. The wires were switched from the reserve Batt to the camper charger. I ran the fridge down twice on 12 volt before I realized something was wrong. Everything else worked just like you say. On the truck side Black to positive post and white to frame. Should be fine on the camper side. I looked and looked but couldn't find it but then I found it going through the truck floor. By sight it was perfect, running my fingers to the wires they were switched.
Good luck!
Joe
Edit, It made my alternator make a high pitch sound. Almost undetectable but after I fixed it it stopped.
