Trailer Light Problems

I just bought a converter for trailer lights for my boat. I followed the instructions and double checked all the wiring. After I got it all hooked up I checked the plug with a meter and nothing was right. I got my dad who is a electrician to check it and he said everything was right. The problem I'm having is when you have the park lights on and you hit the brake all the lights go off. Neither of the turn signals work. According to the meter when I hit the brakes, the ground becomes hot although it is grounded to the frame. Any help would be appreciated.

 

Possibly a bad convertor box

 

Where is the meter connected when you measure the ground as being hot? The normal connection would be to have one lead connected to ground and the other to the point you are measuring. In that case the ground cannot be hot if it is wired correctly. My experience has been that most trailer lighting problems are with proper grounding.