Troubleshooting Non-Functioning Trailer Running Lights  

The running lights worked the last time I ran the trailer, and did not work this time when I hooked up. Storage time 1 week, weather plus minus 5 C. All other lights work. Whenever I test the truck as the source I turn the truck on, manually turn on the lights -they usually sit on auto which is no good, and I visually check to see that the parking lights are lit up on the truck. I disconnected trailer-truck, ran a wire from the trailer positive battery post to the trailer connector for the running lights. All the running lights shine brightly. Checked the truck fuse for the trailer running lights parking lights: it checks out good. check the volts at the truck connector on the parking light post to the truck bumper= 12.?? volts. Plug trailer into the truck just to see, cause Im starting to doubt my sanity or memory or something else, but I forget what that was. No joy, dark running lights all around. I check again see sanity waning from the trailer battery: bright all. I check the volts again = 12.??. I check volts from the truck connector parking light post to the trailer ground 12.?? I check from the truck connector parking light post to the trailer connector 12.?? I run a wire from the truck parking light post to the trailer running light contact in the trailer connector. No running lights: all dark. I hook the connectors together, trailer to truck. no running lights but all the other lights work correctly, except a back up light never did exist. I add a back up light hooking into the trailer ceiling lights, with a switch to turn it on and off. Thats good. But no running lights? Ok, so I am now just a little bit confused as to which universe I just entered. What am I missing? Any help is welcomed. Is this the Delta quadrant suddenly, or warp light Ive entered. Or did I just forget 6th grade science again after 50 plus years?

asked by: Tim