Problems when replacing 7 pin connector

Given that a couple of the wires are heavy gauge and all are fine stranded, I found that it is very difficult to properly install a new connector on a trailer cable. Much easier to replace the entire cable with new molded on plug, making the connections at the splices to the trailer wires.

Charles

deleted duplicate due to connection issues.

deleted duplicate due to connection issues.

deleted duplicate due to connection issues.

^ Good advice there. I’ll just add that once you have the lights wires all identified you can touch one of them to each of the remaining unknown wires. If the lights turn on, that unknown wire is the charge line to the battery.

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.

opnspaces wrote:
Number one hook up the ground wire first. It's most likely the white wire and it's at the 7'oclock position when looking into the socket on the bumper. Once the ground is hooked up you can just play with each wire until you get it right.

I'll try this method next week. I came to an RV park today because when I connected it the second time yesterday, as I wrote above, the trailer battery was completely drained, after just a few minutes. Won't even recharge fully using a generator. So I needed electricity.

I assume I should leave the black power wire for last?

Number one hook up the ground wire first. It's most likely the white wire and it's at the 7'oclock position when looking into the socket on the bumper. Once the ground is hooked up you can just play with each wire until you get it right. But my guess is the

White as ground
Blue as brakes
Brown as tail/running lights.
The other colors will vary, but the positions on the plugs should not vary.

CA Traveler wrote:
Use a ohm meter and check the wiring in the cut off connector then attach the new one the same way ignoring wire colors on the new connector.

This is the easy way and you don't need a helper.

"Don't get mixed up with the mirror image problem for each side of the connection". That is my downfall, e-trailer and others actually have 4 diagrams. One set is for the trailer plug, looking at the face/outside of the plug, plus the reverse/mirror image looking at the back/inside where the individual wires are connected. And the for the tow vehicle receptacle looking into the receptacle or looking at back where the wires are connected.

Ken