The MARKER lights
are on a separate circuit. They operate off the Tow Vehicle tail light
circuit as the brake and turn signals do.
With the Converter OFF meaning U do not have the egg connected to AC:
Take a multimeter and check from the + terminal to the - terminal on the battery
and should you get 12 volts as it should then check from the + terminal of the battery
to the metal frame of the camper. If all is well you will read the 12 volts. If you DO NOT see the 12 volts then you do not have the - side of the battery grounded. On my Scamp
, it uses the frame as a - ground.
If it checks OK then you have an open in the + wiring. Look for a fuse at the battery then look for a fuse elsewhere.
Look for a fuse at the converter.
The following are sites where you can purchase the necessary test equipment should you not have any.