Need help with trailer converter

I bought a toy hauler and when i plug the trailer to a 120volt source the converter does not step it down to 12 volt when connected to the trailer fuse block. I pulled the batteries out of the trailer also because they were only showing 6 volts so i need to replace them.

I then pulled the converter out of the trailer and wired it up so it can be plugged into a wall outlet. It then was putting out 13.6 volts. I reinstalled it back in the trailer, and hooked it up to the fuse block and plugged the trailer back in and it was only reading .53 volts. Is this a sign that the converter is shot? i would think that if that was it the converter wouldnt step it down to 13.6 volts when plugged in to the wall.

any help would be greatly appreciated.

 

Are you measuring upstream of the fuse block after reinstalling?

Pull all of the fuses and measure at each terminal.