[jsb5717]

I'm no electrician either, but it does sound like there is a wiring problem coming from the house or through the cord. You shouldn't be getting 250v inside the trailer. Everything should read at 125v or 12v (post-converter readings). I would be tempted to try using a dogbone adapter that connects only 110v to the trailer to see if that corrects the issue. It's possible, though, that the electrics are ruined in the trailer if it's getting too much voltage from the house.