So, like every job on an old trailer, this one got a bit more complicated. As I redid the battery wiring, I found a few mysteries and a new problem emerged. As I was getting ready to connect the new battery cable to the converter, I found a small device on the side of the old battery box. It sits between the battery and the converter. It's difficult to see but I've decided that it's either a diode or a circuit breaker. I'll try to attach a photo.
The other mystery is a green wire that heads toward the old battery box from the connector for the running lights
. I'm guessing that it is a ground, but the precious owner said she had modified the towing circuit so that it charges the house batteries as it tows. Figuring that out will involve some quality time with a meter.
The problem is with the converter. I pushed the gfci test button and it (the gfci) fell apart. It's an old Carson 15 amp converter and has a terrrible buzz. My next camping trip will be dry (From a power and water standpoint.) my next powered campsite is on Memorial weekend so I'm not In a hurry for a fix.
Here are some pix. The big thing to the right of the terminal strip is a big fuse that sits between the negative side of the battery and everything else.