Trailer With Removable Tongue Not Providing Continuous Ground Connection  

I have a 2006 Jeep Commander with a 7pole with a 4 pole on the side on my jeep. Lights were working last year but not now... When I use my test light on the 7 pole all poles have power when asked. I then plug in the 1st whip to my boat trailer, 7 pole which goes into a 4 pole plug. The reason is the trailer has a removable tongue that needs to be plug and unplugged anytime the tongue is removed. When i use the test light to test the whip from the truck to the tongue I have power for all asked functions. When i plug in the whip from the truck to the last portion trailer I have no lights. I cut that connection thinking that plug on the trailer was bad and tied the wires together, but no lights. Tested the new plug when I plugged it into the whip before twisting the wires together and the test light showed power for all functions...Twisted wires together again no lights. Used a jumper box to test lights. Attached ground to trailer the used my test light through the positive and touched the wires one at a time. All lights worked off the jumper box except the left running light... Why are my lights not working when I plug them in.. Already cleaned the ground by the tongue and tried to use the test light for the ground to the truck....Hope I was clear enough...

asked by: Tony D