Joshc1425 wrote:
1996 northland slide in pick up camper
Probably has a 6300 type converter, which needs a battery to filter the "dirty" 12v to run some things like the fridge's circuit board. The dirty 12v is ok for lights and fans.
What was the replacement converter? If a modern type, it makes only clean 12v and you are ok for no battery as a filter.
Meanwhile you need to get the 12v working on battery for when not plugged in. Also check for 12v when you are plugged into the truck and the truck engine is on.
There should be a fuse or DC circuit breaker on the positive wire near the battery, which is the first suspect. Or just a dead battery.