No marker lights when headlights are on

2013 freightliner Coronado 132 Hey guys I’ve got a problem it’s got me stumped. Ok when I turn my headlights on I have headlights but no maker lights come on. Now when I hit the switch to turn only the maker lights on then they will come on all of them. I have replaced the headlight switch an still I have the same problem. Any thoughts?

 

Thanks klleetrucking im running threw it now.

 

Yes I have tried turning off the main power an also disconnected the battery’s still nothing. I’ve checked all the fuses I’m not seeing nothing.

 

Could the interrupter cause this problem?

 

Marker light switch

 

Tested the markers with the switch in the both positions They only light up when the switch is in the down position witch is running lights only

 

Turns out it was the trailer marker fuse