5 trailer wires

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peiserma

Member
Dirty rotten thief cut off my trailer plug. I thought it would be a simple matter to buy a new plug. But no. There's 5 wires on the trailer. Four wire plug on my car. I know the old trailer plug was 4 wires (i would have noticed if they did not fit, hehe!).

I cant get to the wire junction on the trailer to look at it, it is tucked between the tire and bunk with a boat on top :)

I found a wiring diagram for 5 wire, but that indicates the extra wire is for brakes. I do not have any brakes. Well, not on the trailer, anyways. Is it possible someone just doubled up the brown wire (eg to left and right side) and that is why there are 5?
 
On your trailer you most likely have:

White, ground
Green, right turn/ brake
Yellow, left turn/ brake
Brown, x2 for right and left tails/ marker (one to run down each side of the trailer)
 
Thanks, that configuration was my suspicion. The trailer wires are two duplex pairs. Colors are pretty faded, but they might have been yellow + yellow/brown stripe and green + green/brown stripe at one point. It makes sense, I just wanted a peer check (positive reinforcement). Thats how i rewired the plug, but running lights not working. Thats what prompted this post. Now that i have some confidence that it is correct, i can check the circuit at the car.
 
99.999999999999999999999% of the time it's a ground issue. and 0.000000000000000000001% of the time it's a toss up between a ground or something else.
 
my brand new trailer has a 5 pin plug. Truck is 4 pin. Trailer guy said 5th is for brakes but I dont have brakes so it doesnt go anywhere. They always wire them that way now. He said just plug the 5 pin into the four pin, the dead one will be on the end, not connected.

That being said, I think the fifth wire in your case is the second brown wire. They get tied together to connect to the same pin on the plug.
 
Last edited:
SkunkBoat said:
my brand new trailer has a 5 pin plug. Truck is 4 pin. Trailer guy said 5th is for brakes but I dont have brakes so it doesnt go anywhere. They always wire them that way now. He said just plug the 5 pin into the four pin, the dead one will be on the end, not connected.

That being said, I think the fifth wire in your case is the second brown wire. They get tied together to connect to the same pin on the plug.
Click to expand...
It's isn't for brakes directly, it is for your reverse lights. When in reverse you want the brakes locked out so you can back up(hrdraulic actuators get engaged by the trailer pushing against the tow vehicle and applying the hydraulic actuator, reversing does the same thing to it), so the reverse power goes to a solenoid in the brake system to keep them from activating.
 
That would be for a 5 TERMINAL plug... he stated that he only had 4 terminals and five WIRES.... it's two tail light wires for a split harness
Traildia_small%20copy.JPG
 
Yes, my trailer has two brown wires like the diagram. Only they aren't colored brown (see previous post). The problem took longer to find than anticipated. I have a Hopkins Power Tail Light Converter in the car. The wire that picks up the tail light signal wasn't installed properly and had come loose. Fixed that, and all the lights work now.

Thanks for the help.
 
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