Good afternoon all, yesterday I picked up a used boat. The trailer wiring near the connection that hooks to the vehicle was pretty bad so I took some initiative to replace it. It was a 5 wire connector that went into a 4 pin adapter. I picked one of those up and began to rewire. Once I was done, I did a walk around to see if everything was in working order. The issue that I'm having is pretty strange and I think it could be fuse related. Looking at the rear of the boat, the left running light (driving) doesn't work. This lights blinker and brake light do work, however. The right running light does work, but the brake and blinker do not. Both side markers do work. It appeared to have functionality when I left with the boat from the seller. Anyone have any insight on what this could possibly be?

first check grounds. also check sockets where bulbs go,if that is what kind of bulbs you have.otherwise double check the 4 to 5 pin connector.

The brake lights are the blue wire. The directional lights have 2 wires, 1 yellow for left and 1 green right going to seprate contacts, running lights and tail lights. are 2 wires to 1 contact= 4 wires, 3 contacts and 1 white ground wire going to a contact = 4 contacts for the trailer.

Tom

Thanks for the reply, the wires coming out of the trailer were green, brown/yellow, brown/green and yellow, with white being my ground. Its clearly drawing power, but for some reason I can't have universal functionality, just either or across the two lights. The only difference in the other adapter that I disconnected is that it had two wires going into separate holes in the adapter, the new one has the two brown ones connecting literally in the same port but still has 4 pins. I'll try to get pictures to clarify all of this. 

If you have standard bulb type lights,do yourself a favor and buy some LED submersible units for about $50.Well worth the the $$

As said already, grounds account for many problems

Thanks Catch22, the fuse in fact was the issue on the right side. I'll likely find its an issue of grounding on the left side, I'll update when its solved.

On 9/3/2016 at 5:31 PM, RGRFish said:

Thanks for the reply, the wires coming out of the trailer were green, brown/yellow, brown/green and yellow, with white being my ground. Its clearly drawing power, but for some reason I can't have universal functionality, just either or across the two lights. The only difference in the other adapter that I disconnected is that it had two wires going into separate holes in the adapter, the new one has the two brown ones connecting literally in the same port but still has 4 pins. I'll try to get pictures to clarify all of this. 

So, to make things simple, (just restating something already said) you will have white, brown, yellow, and green wires.

Green - right turn

Yellow - left turn 

Brown - running lights (the two brown wires on the trailer connect here) 

White - trailer ground. This gets mounted anywhere on the trailer that is clean of rust/paint. 

Once you make sure these are all connected, most trucks will have a trl prk, trl lft, trl rt, and possibly a trl brk. These fuses are trailer park lights, trailer left turn, trailer right turn, and trailer brake. 

If you have running lights on one side and not the other, you either have a bad connection/broken wire on the trailer somewhere, or something isn't wired right.