I am trying to get my lights to work. I have a 24ft enclosed trailer I use to haul my race car. I have a 27ft class A that pulls it. The trailer was a toyhauler that was gutted out before I bought it. A friend helped me by using his Ford pickup to go get the car and trailer and all the lights and brakes worked great. But my Motorhome I can't get the lights to work. I have power 12.95 amps coming from the RV but the lights don't come on. The trailer has a battery and if I run a wire from that to the plug the lights work. I thought that I wasn't getting a good ground on the RV so I connected jumper cables to the RVs frame and to the trailer frame but the lights still don't work. The plug has 6 tabs and a ground in the center.
The plug on the trailer or RV are not lining up properly, or the lights would be working. From the top, count to the right one or two or three places to find the + 12 Volts from the RV when the parking lights are on. Then on the trailer, count the other direction to find the same plug point, and apply 12 volts from the trailer battery should turn on the lights. Once both are on the same connection, then it will work.
With my RV and my brother's trailer, the RV was drawing about 13 amps to run the lights, and the trailer was another 10 amps, so the 20 amp fuse kept blowing. Also I was only measuring 9.75 volts at the back bumper while hooking up the lights (engine off). So I used a 12 volt relay to power the trailer light plug wire, and already had a wire coming from my coach battery back to the bumper, so 12 volt battery went into the contacts then to the trailer connector, while 12 volts from my running lights went to power the relay coil, and the other side was grounded, so the relay is on when the running lights are on.
I found the wiring diagram for the plug and it was the same way I was wiring the plug. Except I was using the center pin for the ground. I am not using the center pim anymore as a ground. What I can't figure out is If I take a wire that is connected to the battery that is on the trailer if I touch a pin on the trailers plug the lights come on great or the left tail lights or rights. Now the RVs plug has the pins lined up correctly and have power to them but no lights come on when I plug the two together. The running lights on the motorhome are bright but the low beams seem to be a little dull.
Since the lights etc. worked fine behind your friend's truck, sounds like the trailer is correctly wired. It seems logical that the problem is with the motorhome connection. If it's using the center pin for ground, that's another clue it's wired weird- as pointed out above, that pin is almost always "reserve".
" Not every mind that wanders is lost. " With apologies toJ.R.R. Tolkien