7 Pin Wiring Issue Marker and 12v Aux swapped

[Gpagolf]

When I have my trailer plugged in and the truck is off and trailer marker lights stay on all the time.

I put a test plug into the bumper and the bed 7 pin plug the TM lite pin lights up and the 12v Aux was dead. But all others were as expected. Any idea what to do? I am thinking it is from wherever these wires terminate they got swapped. Just not sure if there is a controller or just straight run to the fuse box.

I would like to fix at origin so don’t have to cut wires on two plugs.

 

[joesstripclub]

Not sure what you're trailer looks like, but there should be a junction box where the 7-pin cable ties into the trailer wiring. That's where I would start if I was you. I agree it sounds like a couple wires were flipped.

 

[18CrewDually]

Make sure you're testing the correct pins. It could be (more likely) your trailer is wired wrong or wires inside the plug are touching each other.

 

[wrench78]

Not sure what kind of trailer you're talking about. But utility trailers can be wired differently.

 

[18CrewDually]

Not sure what kind of trailer you're talking about. But utility trailers can be wired differently.
View attachment 546708

No, they are all wired the same. The terminals are all defined same on a 7 - way plug regardless.
Wire color can varies but I've seen all kinds of variations. Never trust the colors. When in doubt, Ohm it out!

 

[wrench78]

No, they are all wired the same. The terminals are all defined same on a 7 - way plug regardless.
Wire color can varies but I've seen all kinds of variations. Never trust the colors. When in doubt, Ohm it

 

[wrench78]

No, they are all wired the same. The terminals are all defined same on a 7 - way plug regardless.
Wire color can varies but I've seen all kinds of variations. Never trust the colors. When in doubt, Ohm it out!

oh yah, I see it now. it's the colors that are different, not the locations.

 

[18CrewDually]

oh yah, I see it now. it's the colors that are different, not the locations.

Yes. And fun fact, most lids of the plug receiver (truckside) has a pinpoint label of each pin too.

 

[Gpagolf]

Definetly the truck and not the trailer. In addition, the light switch to turn lights off and the marker light switch are reveresed on the truck.

View attachment 546662

Make sure you're testing the correct pins. It could be (more likely) your trailer is wired wrong or wires inside the plug are touching each other.

100% not the trailer.

 

[2003F350]

Definetly the truck and not the trailer. In addition, the light switch to turn lights off and the marker light switch are reveresed on the truck.

100% not the trailer.

If that's the case, it needs to go back to a dealer and be fixed under warranty, presuming you are still under mileage. It should NOT have left the factory with the wiring messed up that badly.