1999 Chevy Suburban

Trailer Wiring Question. I have a 1977 Shasta trailer. All lights on the Suburban work fine, but the running lights on the trailer don’t work. They did at one time, but not now. The brake lights, turn signals and hazards work fine, but not the running lights. I tested the 6 pin connector on the Suburban and the I’m getting power to the running light post. (Of the 6 posts this is the top middle that shows power.) What’s strange is I only have four wires coming out of the trailer connector. (See Picture)

When I test these wires with my circuit tester I get power as follows: Blue Wire – Left Turn Signal. Brown Wire – Right Turn Signal, Brown Wire – Hazards, Brown Wire – Brake Lights. I get no power from any wire when I turn on my head lights. (I assume the black wire is my ground as it is connected to the trailer.) The 6 pin female connector on the trailer may be bad, but I wouldn’t know what to replace it with that has only 4 wires… I’m leaving for vacation in a few days and don’t have the time or expertise to rewire the whole thing. As you can tell, I’m pretty clueless on mechanical/electrical stuff so any help you can offer will be appreciated. Also, I bought both the Suburban and the trailer used and didn’t have anything to do with the wiring on either.