I have metered the output from the converter and it reads +13V. I metered the battery and it reads 12.7V! With battery connected, all 12V systems work. When I removed the positive line from battery, nothing works. It seems the converter is not really connected to the 12V system. The 120v plug does work.
What am I missing? Shouldn't the converter by supplying charge to the battery (seen as a >12.7 voltage) and power to the trailer?
Yes, the two are connected in parallel and either should run the 12 VDC loads. Follow the converter voltage with your tester (battery disconnected) and you will find the problem. (Fuses and Scamp splices are common failures.)
Found the issue. One of the ground lines under the trailer had broken loose. After reconnecting it, everything looks good.
The under carriage writing of the scamp seems quite exposed. I've had to reconnect a break wire in the past as well.
This is how we learn.