Trailer wiring HELP needed.

[rev500ss]

Ok folks hopefully someone can help me and quickly.
I'm having wiring problems with my 5er.

I've tested my truck and have power, signals, brake lights etc on my 7 way, but I plug my trailer in and I get nothing. No lights no brakes nothing.

I was supposed to leave on my first trip of the year this morning and I'm still sitting in my driveway 😭

I last towed my trailer back in May and lights and brakes were working fine then.

Please HELP!

[66joej]

You can try using a jumper on your cord. Put it on the top 2 blades (looking at the plug). You should light up your running lights. If this works then you need to make sure the the blades on your plug and pins on the truck are clean. Spray some WD40 as a temporary fix.
I'm thinking you have the trailer battery hooked up for this.

[Daryles]

Try this
https://www.google.com/imgres?imgurl=https://i.pinimg.com/originals/14/18/e2/1418e22fb585f177f216b8292eeb1fb5.jpg&imgrefurl=htt ps://www.pinterest.com/pin/557531628867276611/&tbnid=xUH7WUJGFktrFM&vet=1&docid=MkUB36EzgDkTkM&w =960&h=1469&itg=1&hl=en-US&source=sh/x/im

[rev500ss]

Thank's guys, tried the jumper still got nothing.

Can anyone take a picture of the wiring in the electrical box on their pin box? I think that's where my issue is.
I ended up getting by brakes to energize but still no lights.

[66joej]

Just my opinion but before I started pulling on wiring check to make sure you have a good ground with the trailer cord. I have found a lot of no power is often a poor ground.

[rev500ss]

I've checked, removed, cleaned and re attached all the ground I could find, still no lights.
I just don't get it, nothing has changed since it was parked but yet nothing works now.

[Daryles]

Any chance the trailer battery has anything to do with it? Battery disconnect switch?

[chuckster57]

Using the color codes above, I would open the junction box. Using a VOM verify that you have 12VDC between the black and white. Often times there is a large number of white conductors in one wire nut. Then start testing circuits.

[rev500ss]

This particular trailer doesn't have a battery disconnect switch.

All the info is great so far but I'm not the greatest with wiring so I really have no clue where to start.

I had a trailer mechanic come and fix the wiring (similar issue) last year, but it seems to have come back.

There are far too many connections in my electrical box on my pin box for me to understand.

What color is my positive?
Which is my netural? Positive? Which are my running lights?
I know with my snowmobile trailer (4 wire) the yellow and brown and green were my running lights/brake lights and turn signals, but this 5er has got too many options.

[chuckster57]

Black is positive
White is ground
Blue is brakes

After that my color blindness forces me to get someone else.

I understand it can look daunting and intimidating, but trust me it isn’t. Like I said before, there may be a bunch of whites crammed into a very large wire nut and sometimes one will back out losing contact.

When looking at the blue (brakes) you will notice a black connected. That’s the break away switch. One of the blacks will go from the black coming from the battery, to the break away switch and then to the blue.

After that the running lights and brake light/turn signals should be single wires.

If your junction box uses wire nuts, I would take each one apart ONE AT A TIME. Be careful when you undo the black as it will be 12V LIVE so don’t let it touch the box or ground.

[rev500ss]

Thanks this will help! I'll get back at it in the morning. At this point I've turned to my friend Budweiser and won't be going anywhere tonight.

I think my specific trailer has red, white, green, blue, black and yellow all mixed in. I tried to attach a picture, but it didn't work.

[chuckster57]

If the yellow from the umbilical cord is used, that’s normally used for back up (reverse) lights.

I’ll be at work tomorrow, have to do a walkthrough on a Tiffen Phaeton (look it up) so I may be tied up for a few hours. I’m sure someone will be around to answer any questions.

[Larry4545]

Dc voltage can act crazy when checking it with a digital volt meter. The meter has high resistance and does not introduce a load on the circuit when testing. So when testing you can read a voltage but then when you apply a load such as your trailer the voltage disappears. This is cause by a faulty connection usually on the truck side.
I had this issue on my F250 on the plug. There is a plug on the truck harness wiring that plugs into the actual trailer plug. Make sure all is ok at the bumper.

[rev500ss]

Ok, was back at it for the better part of the day and still not much progress.
I have power 12v into my junction box on my pin box.
From there I don't seem to be getting power through the wires to my lights.
I made a couple test leads and used another 12v battery and can get my marker lights to come on, I can light up the tail lights and had brakes yesterday after messing with the wires.
Can someone please explain how this is possible?
I just don't understand!

[JRTJH]

First, from what you stated, you may be thinking that the power source for each of those light functions is the +12VDC that is in the mix. NOT SO !!!

The ONLY thing that +12VDC powers is a small charge line to the battery, the break-away switch and the tongue jack. Everything else is powered by the truck, through the individual wires at the 7 pin connector (on the truck) and when the trailer is plugged in, through the 7 pin connector to each of the functional light systems....

On the truck is the following:
#1 pin is GROUND
#2 pin is TRAILER BRAKES
#3 pin is TAIL/RUNNING LIGHTS
#4 pin is +12VDC (charge line, trailer tongue jack, breakaway switch)
#5 pin is LEFT TURN/STOP LIGHTS
#6 pin is RIGHT TURN/STOP LIGHTS
#7 pin backup lights (on Keystone, normally not used)

NOTE: The pin numbering is not sequential, so pay attention to the diagram that I've attached....

Essentially the only purpose of that "junction box" that you've posted photos of is to connect the wires from the trailer to the wires from the 7 pin/7 wire umbilical cable. There is no "electrical switching or electrical management" in that box, it's only a means to house the twist cap/squeeze connectors so they don't corrode or fall off during travel...

So, when you state, "I have power 12v into my junction box on my pin box.
From there I don't seem to be getting power through the wires to my lights."

If you're thinking that there's some "inter connections" in that junction box that control the distribution of power" then that's not its purpose.... ALL IT DOES is act as a place to connect wires. Each of the wires from the trailer, through the 7 pin connector, to the umbilical cable, to that junction box is a separate and distinct circuit. If the truck isn't providing power to the blue wire on the 7 pin connector (pin #2) you won't get any power to the trailer brakes, if the truck isn't providing power to the brown wire (pin #3) then you won't get any tail/running lights... and so on through each of the circuits.

So, if you turn on the truck ignition (most trucks won't provide power to the 7 pin connector unless the truck is running) and turn on the headlights, you should have power on pin#3 and the brown wire in that junction box should have power. If not, unplug the 7 pin connector and check for voltage from the truck. Present, then it's the trailer, missing, it's the truck.. And so on through each of the functional light circuits.

Although you can "jumper within the junction box" or "jumper at the trailer 7 pin plug, you need to verify that the truck is providing power (with the engine running) before you go any further, then work back toward the trailer systems...

In other words, no power from the truck, no power at the trailer junction box.

[rjniles]

Buy a 7 pin test light from Walmart and check to see if the truck wiring is working.

https://www.walmart.com/ip/Truck-Tra...EaAoDNEALw_wcB

[66joej]

Just a wild guess but have you checked the truck trailer fuse. Usually under the hood.

[LHaven]

In the first post, the OP stated he had tested all his truck outputs and they were OK, so I've been taking that for granted. If that turns out not to be the case, the diagnosis would be very different.

One simple test would be to pop the battery box cover and run a test lead between battery + and pin 3 on the trailer's cable. If the running lights don't immediately come on, that would square with everything else that has been claimed so far. If they do, then I'd go back and take a hard look at the truck.

I hope it's not something simple, like the plug sticking halfway into the truck socket and the OP assuming it has bottomed out. I know my own plug can give me lots of backtalk before it pops the rest of the way in, far enough for the prong on the cap to lock it in good. But I see upon re-reading that he's towed this trailer before, so probably not.

[ctbruce]

Ok, I'll ask. Is the pin inserted all the way and the cover locked down on the tab? It is possible to connect them wrong. Don't ask how I know this.

[rev500ss]

I have a 7pin tester and it's showing that everything on the truck end is good.
I have also gone through all the fuses and they are all ok as well.
I have been using a 7pin connector on multiple trailers for the last 15 years, so I'm not new to trailering or connecting my trailer.
I have power at my truck, and when the trailer is connected I get power into my junction box. I don't understand how my lights are still not working.