Leaving a specific wire for last isn't much of an issue. But it also won't hurt anything if you do.
Thinking about this further and assuming you do not have a meter this is what I would do. It's just a process of elimination.
Pull ALL the wires out of the replacement plug.
Take a pen and paper and write down the color of each wire in a vertical column.
While a helper stands behind the RV with the pen and paper touch each wire one at a time in the following order to the positive post of the battery. Have you friend observe the lights and write down which light corresponds the each wire.
Brown
Yellow
Green
Red
If only one tail light comes on that is a turn signal.
If both taillights and the top lights come on that is the running lights.
Once you find the two turn signals and the running lights you're in pretty good shape. though you'll be making a few assumptions.
Assume white is ground
Assume blue is electric brakes
You tested and found
Yellow (maybe left turn)
Green (maybe right turn)
Brown (maybe running lights)
That leaves only one maybe two wires to figure out. (charge and backup lights) Most trailers do not have backup lights so you're really only looking for one wire. But without a meter you're going to have to guess.
Hook all the wires up the and pick a left over wire and hook it up in the charge position of the plug.
Now plug the cable into the tow vehicle and turn on the ignition. Check that all the lights now work. (If the left and right turn signals work that also checks the brake lights)
To test the charge wire unplug the umbilical from the vehicle. Turn on the porch light of the trailer. Start the tow vehicle engine and let it idle.
While someone is observing the porch light plug in the umbilical. If the porch light gets brighter you have correctly identified the charge wire. If not then
A) check the fuse)
B) Swap with the other leftover wire and test again.
.
2001 Suburban 4x4. 6.0L, 4.10 3/4 ton **** 2005 Jayco Jay Flight 27BH **** 1986 Coleman Columbia Popup
