I'm having a terrible time with wiring for a Donahue gooseneck stock trailer I bought used. The trailer's 6 way round worked fine directly with her Ford diesel she hauled with. Unfortunately, I don't have a 6 way receiver on my 2500, so I bought a 7 to 6 adapter; when plugging the trailer's end into the adapter, things just didn't work properly.

So, I used a test light to figure out what hole operated what in the adapter. I hope this shows up correctly when I post it, but I'll try to diagram it here:



The trailer only has five wires to the male end - red/12V, black/ground, brown/right turn, yellow/left turn, and green/running lights? So, one hole has nothing to it. I've tried wiring things so that these colors line up to the adapter's functions: yellow to left turn, brown to right turn, red to 12 V, black to ground, and green to running lights, but then there was no trailer brakes (of course). I put green to the e-brake center hole, and I got numbers on my brake controller when I hit the brakes, but the brakes were locked up and I dragged the trailer!

Inside the trailer there is a box with splices making things even more confusing to me. There's no blue wire in the cable going to the male trailer end, but the cable goes into the box where 6 wires come in from the various trailer functions - there is a light blue wire, and there is an aqua green wire, in addition to the regular green for the running lights. The following splices are made between the trailer and the cable going to the male end: black to black, red to red, yellow to yellow, brown to light blue, black to aqua, and aqua then continues on the splice with green!

It's maddening that the manufacturer didn't just put a sixth blue wire in the cable! So, how should I wired the trailer end to jibe with my adapter properly such that I get e-brakes AND running lights without brakes locking up?!

I hope this made sense!

 

Neither of those wiring patterns are correct for the standard wiring of a six-prong plug.

The center hole is an auxilliary terminal and should be marked AUX.

The largest diameter terminal should be marked GD for ground.

Looking into the truck portion of the plug, under the lid, looking in, proceeding clock-wise from the GROUND, LT = left turn, RT = right turn, S = supply from trailer-brake controller, TM = trailer markers = tail lights and parking lights.

If the plug is wired properly, it will work on any truck, or trailer, that is also wired properly, as all brands of six-prong plugs are marked identically.

If you will dis-assemble both plugs, the terminals will be marked with arrows pointing to the appropriate terminal.

Dumbies just wiring plugs hap-hazzardly, without following standard wiring patterns, should not be allowed to pick up a screw-driver.

 

If re-wiring the plugs properly is a little over your head, then you can simply correct your problem inside the box on the trailer.

It will only work with your truck, as it will not be wired standard.

Take all wires apart in the box on the trailer.

Identify which wire from the truck is each function and connect it to that function in the trailer box.

Does any of that make sense??

 

BearKiller is right - and I would definitely advise rewiring the plug properly (and the junction box if req'd) so any correctly wired vehicle can power it.