7-pin connector wiring. Unusual problem getting running lights working.

[zack sc]

I have read about 7-pin connector wiring and I thought I understood it pretty well, but I am having a sort of unusual problem that has me stymied and would love to get advice.
So I am re-wiring my seven pin connector on the trailer side. And I’ve got everything working except for the running lights. I had to figure out the color scheme from scratch because the old plug was gone. What I have is: Black is 14 V, white is ground, Brown is right-turn, red is left-turn and yellow is back up lights. I have tested all those and they seem fine. Additionally, I can see with a voltmeter that the pin just to the left of the 14 V is for the lights, and it seems to be working, showing 14 V when I turn on the TV lights, and 0 V to ground when I turn off the tow vehicle (4Runner) lights.
Additionally, I’ve measured the resistance to ground for all the colored wires going into the Scamp and they are: 2.1 ohms for red and green, 2.3 ohms for brown and yellow, and 3.3 ohms for blue. So I figured the blue wire is the brake controller and the green wire is supposed to be the lights. But I can’t get the lights to work; and I’ve tried the blue wire as well, but I think that’s for the brake controller, like I said. There is one odd thing: maybe I should’ve mentioned right in the beginning: the green wire, when you strip it is pretty black; all the other wires are shiny coppery looking. I’m not sure what that means or if that’s connected at all to my inability to get the lights to work. But the thing is the green wire to ground does show 2.3 ohms which seems like a respectable value for going through some lightbulbs. So anyway I’m a bit stymied and any help is appreciated.

[Casita Greg]

This is a standard 7-Pin connector, and shows which wires should go to which pins. As to what colors the factory actually used for different circuits is something you'll have to find out by testing. I know that my Casita doesn't follow most established "color codes" for trailer wiring, so I have had to trace out which trailer wire colors go to what. And don't discount that you may also have some grounding issues, which are very common in trailer wiring, and those will also compound your problems if they exist. It can be a bit of work to get it all straightened out.

[zack sc]

Thanks Greg. That is exactly the wiring pattern that I found. I am worried about grounding issues but I checked the polarity of the 13V at the battery leads and it is the same with AC and DC power. So I am not sure what I would do.

[Raspy]

This doesn't seem like a grounding issue, but it would be a good idea to make sure it's not by grounding the trailer to the Tow. This could be as simple as attaching a jumper cable from the tongue to the tow frame, or testing all hot wires to the trailer frame. See if there is a ground lug that combines a 12v negative battery ground, a trailer brake wire ground and a lighting ground. Trailers used to be grounded through the hitch!

If the green wire is tail lights, and it is possibly bad, go to the tail light socket and test from there to the green at the seven pin. See if that wire is continuous or not from the bulb socket to the front of the trailer.

[zack sc]

Originally Posted by Raspy

This doesn't seem like a grounding issue, but it would be a good idea to make sure it's not by grounding the trailer to the Tow. This could be as simple as attaching a jumper cable from the tongue to the tow frame, or testing all hot wires to the trailer frame. See if there is a ground lug that combines a 12v negative battery ground, a trailer brake wire ground and a lighting ground. Trailers used to be grounded through the hitch!

If the green wire is tail lights, and it is possibly bad, go to the tail light socket and test from there to the green at the seven pin. See if that wire is continuous or not from the bulb socket to the front of the trailer.

Thanks. You know in the tail-light housings, which I have taken off, there are two bulbs. The upper one is for the back-up lights I think. The lower one has two separate filaments. One of them lights up when I do turn signals and brakes, the other filament does not light up. But the green wire to the ground at the trailer 7-pin shows 2.3 Ohms, which suggests to me that there is continuity. I am thinking that the lights on the side, are running lights that should go on whenever I turn the lights on in the tow vehicle. Is that correct?

[Lynn Eberhardt]

Yes. All running lights, side and rear, should come on with tow vehicle lights.

[Raspy]

Yes. As Lynn said, the side marker lights and the tail lights, should all come on together. They should come on with the tow vehicle headlights or parking lights.

[AC0GV]

Originally Posted by zack sc

I have read about 7-pin connector wiring and I thought I understood it pretty well, but I am .

With it unhooked from the tow vehicle, Jumper from 4 to 3 on the RV and use your volt meter to find out where the voltage is lost. 4 to 3 will light the lights when all is well. (when you plug a flasher in those two the lights flash also, that's how they do it at the shows.)

[zack sc]

Originally Posted by AC0GV

With it unhooked from the tow vehicle, Jumper from 4 to 3 on the RV and use your volt meter to find out where the voltage is lost. 4 to 3 will light the lights when all is well. (when you plug a flasher in those two the lights flash also, that's how they do it at the shows.)

So, if I understand correctly, basically you’re saying I can put 14 V between the wire I think is the lights and ground and test it that way. That sounds good to me.

I don’t really know the numbering system, but on my connector starting at 9 O’clock and going clockwise, I have: Left turn, running lights, 14 V, right turn, brake controller, ground.

[zack sc]

I am guessing that 3 is the lights and 4 is the 14 volt. So that would make 2 the left turn signal, and 5 the right turn signal, if I understand this

[AC0GV]

Originally Posted by zack sc

I am guessing that 3 is the lights and 4 is the 14 volt. So that would make 2 the left turn signal, and 5 the right turn signal, if I understand this

The lights should already be grounded, just hook the 12to14 volts to the light wire of the light that you want to light. I use my amp meter as the jumper.

[zack sc]

Using the amp meter as a jumper is a really cool idea. I wish I had thought of that and done that because then I could’ve seen the current as long as I was jumping. Anyway I did jump it, and the lights did light up as soon as I applied to 13 volt.

So does that mean maybe a blown fuse in the tow vehicle?

[AC0GV]

Originally Posted by zack sc

Using the amp meter as a jumper is a really cool idea. I wish I had thought of that and done that because then I could’ve seen the current as long as I was jumping. Anyway I did jump it, and the lights did light up as soon as I applied to 13 volt.

So does that mean maybe a blown fuse in the tow vehicle?

Yes, or a bad contact in the plug. Has it ever been hooked to another trailer?

[Randyag]

I have had many enclosed trailer and worked on boat trailers. Those trailers brown was running lights white was ground yellow was left brake and turn. Green was left turn right and brake. The way we remember was yellow had L in it for left and green had a R in for right. Maybe your trailer was wired old school. This was also the wiring code on older Chevy trucks and vans Good Luck

[dfandrews]

Regarding colors, there are two 7-pin standards.: traditional utility trailer, and, RV trailer. My Escape trailer uses the RV standard, as does all the travel trailers I've ever helped friends with.

etrailer.com shows the two: https://www.etrailer.com/faq-wiring.aspx
scroll down to the 7-pin photos. Here's one:


(Edit: A long time ago, I printed out a copy of the etrailer image, and I have it taped to underside of the lid of my trailer tool box. even though I remember the colors & pin outs, it can help when you're tired, in the dark, on the road, and the lights are funky!)

[Rick M]

PLug your trailer into the truck. Than turn on left signal see what lights come on than right signal see what lights come on. This will tell you pretty quickly if your truck is wired correctly. I would even try your break controller,You never know. When you put a jumper between 3 and 4 and lights come on your trailer is fine. The problem is in your tow vehicle. Good luck.

[gordon2]

Originally Posted by dfandrews

Regarding colors...

Regarding colors, never trust them.

Originally Posted by Rick M

... I would even try your break controller,..

But its already broken.

[Joe Romas]

Regardless what color coding your harness and plug uses the "traditional" and "RV" standards have the same pin assignments.
The color of the copper wire inside the green insulation being black means it's corroded.
Just replace it with a cable with a molded on connector. Last time I looked even Wal-Mart has replacement cables and the one I bought even used the "RV Standard" color coding. Here's one on amazon.
https://www.amazon.com/Trailer-Repla.../dp/B00UIOIP0K

[zack sc]

Originally Posted by AC0GV

The lights should already be grounded, just hook the 12to14 volts to the light wire of the light that you want to light. I use my amp meter as the jumper.

Thanks very much everybody! It is totally working now. The technique of using the meter in amp mode to jumper things is so cool. It seems obvious now, but I never thought of it myself, so thank you! With the test leads just resting in the trailer side connector, contact between 3 and 4 was made easily and I was able to walk around the scamp and see all the lights working and then see that it was drawing about 2 amps as I recall? Maybe 1.7 amps. Which seems reasonable.

The problem was apparently in the tow vehicle. In the TV I took out both fuses that said towing; they had continuity and looked fine, and after I put them back in place everything worked. One of the fuses, a 40 A, was a big square green one. I don't have any spares of that kind and I wondered what that is, what it is called and what to buy as a spare. (The other one was the same as the dc fuses in the Scamp, and I have lots of those.
Two last questions if I may:
1) A lot of the time I would pull the 20 A fuse on the battery plus wire just to be safe. Is that a good practice/important to do? Sometimes I forgot. Could I have gotten a shock if I had touched the 13V and the ground in the wrong way? I am guessing that those are connected to the battery in order to enable charging when you tow.
2) While I was working, I had the fridge going on AC power, so I was connected to shore power, and at least a couple times I forgot to disconnect that when I connected to the 4Runner and started it in order to test things. So there were kind of two sources of power at once. Is that pretty bad? What can happen? Should I be really attentive to avoiding that in the future?

[Joe MacDonald]

Two last questions if I may:
1) A lot of the time I would pull the 20 A fuse on the battery plus wire just to be safe. Is that a good practice/important to do? Sometimes I forgot. Could I have gotten a shock if I had touched the 13V and the ground in the wrong way? I am guessing that those are connected to the battery in order to enable charging when you tow.

Install a master switch, turn it off when working on anything battery or 12v electrical
You probably would not have gotten a shock, but you could pop a fuse, or worse cause an electrical fire

2) While I was working, I had the fridge going on AC power, so I was connected to shore power, and at least a couple times I forgot to disconnect that when I connected to the 4Runner and started it in order to test things. So there were kind of two sources of power at once. Is that pretty bad? What can happen? Should I be really attentive to avoiding that in the future?

Both electrical systems are supposed to have blocking diodes to prevent any issues, but i generally try to remember to unplug, don't sweat it

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