Trailer wiring

[Jaime]

Hello,

So I decided to tackle the wiring On the truck going to the trailer. It has a seven pole and a round four pole. The seven pole only has wiring going to the brake controller. The four pole wiring does not go to the lights it goes towards the cab behind the fuel tank and disappears. My question is this normal or has a previous owner monkey it up. The lights work but not properly.

[Eagle]

Those are both aftermarket sockets, so the previous owner definitely monkeyed with it.

 

What's improper about the way the lights work?

 

[Jaime]

The brake lights (work), running lights (only the right side comes on), left turn signal (works), right turn signal (both lights come on), hazard lights (both flash), I put a probe light to the socket on the truck and it works as follows top right (right turn signal), bottom right (left turn signal), top left (running lights), bottom left (nothing so must be ground), brakes (both right & left prongs light). I’m starting to wonder if it’s not the adapter that is wired wrong. It doesn’t look home made. I might try and see if I can take it apart. Oh I forgot the adapter goes from round to a flat. Do you know what color wires are supposed to what connection?

[Dammerung]

The brake lights (work), running lights (only the right side comes on), left turn signal (works), right turn signal (both lights come on), hazard lights (both flash), I put a probe light to the socket on the truck and it works as follows top right (right turn signal), bottom right (left turn signal), top left (running lights), bottom left (nothing so must be ground), brakes (both right & left prongs light). I’m starting to wonder if it’s not the adapter that is wired wrong. It doesn’t look home made. I might try and see if I can take it apart. Oh I forgot the adapter goes from round to a flat. Do you know what color wires are supposed to what connection?

I had a trailer brake unit installed on mine by a previous owner. Rear lights also didn’t work. I would redo the ground connections because that was a major issue with mine, as the factory connectors suck. Also check the ground behind the driver side taillight. It was giving me issues so I sanded the metal down and put a bolt and nut through it, though I’d recommend relocating the ground.


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[Eagle]

 

[Jaime]

Well thanks to you guys, I got it to work. Opened the adapter and figured out that the green and brown wires were in the wring pins. Now I don’t know if the adapter was wired wrong or the plug on the truck is wrong. The adapter looks like a store bought one. The plug on the truck is riveted to the bumper so I can’t pull that apart and check the colors. On my next day off, I am going to cut the wires to the small plug and hook it up to a 7 pole with a 4 pole plug on the side. I was hoping to rent a pop up from the base this summer but it looks like that’s not going to happen this year, since the base is shut down to retirees because of COVID19. Maybe next year!

 

Thanks again!

[gogmorgo]

Trailer wiring seems to be janky as a rule. 
While there is a standard colour set for 7-wire trailer wiring, you can’t always rely on the person who wired it to get it “right”. And “right” is in quotes because there’s two separate colour schemes in use in North America. In Eagle’s diagram you’ll see the labels (words) don’t match the colours. The labels are the more common RV style, while the colours themselves correspond with the other one. And to add confusions, the made-in-China trailer plugs we buy in bulk at work are labeled in a way that doesn’t correspond with either. 

I personally would get the 7-wire socket working on the truck and leave it at that. The round 4-wire connector is getting pretty uncommon for actual trailer connections anymore, but the flat-4 connector that is common is pretty susceptible to dirt and corrosion when left on the back of the truck. 7-way to flat-4 adapters are cheap enough if you do ever need one.

[Jaime]

So I took gogmorgo’s advice and used the existing 7 pole.  I used a 7 to 4 pole flat works like a charm. I have no way to test the brake controller but the lights work.

 

Thanks again!!!