[Roadsters] Roadster Trailer Lights Connector Wiring Question

[aiken1315 at bellsouth.net]

I built a small cargo trailer to pull behind my roadster to The Mitty.  I have wired the trailer 4-prong wiring connector to my car tail light wires and can not get both the trailer running lights and brake lights to work together.  Blinkers hooked up easily and are good.  There are two wires and a ground wire that go to the tail lights.  Using process of elimination I initially tried wiring the tail light connector wire to each tail light wire separately and they would only worked separately (duh).  I then spliced the wire from the tail light connector and attached each spliced wire to a tail light  wire and still only the brake lights work - no running lights on the trailer.  Any suggestions or experience in getting both to work? I know everyone has experience pulling a trailer with a roadster :>).

David 
Daily driver 66
Rusted, but titled 67.5 and a completely torn down 70 in the garage that my wife keeps asking questions about