Trailer running lights

[Krmp]

So this may have been discussed already some where in the forum, but I couldnt find it. I have a 2016 turbo diesel Laramie package. Having trouble trouble shooting the left rear tail light on my boat trailer while it is plugged into the truck. The turn signal/brakelight work, but the tail light doesnt light. I wired a 12 volt battery into the system discounted from the truck and the tail light works. Should tell me that a truck fuse is blown however I did have running lights on the whole system when plugged into the truck. Sorry this is so long.

 

[GTyankee]

Either look online or at a trailer/boat store around your area

There are several companies that make trailer Simulators

It plugs into your trucks trailer plug
it has 7 led bulbs
It basically helps you to pinpoint wiring issues

How To Test 7 Way Trailer RV electrical Plug

How To Test 7 Way Trailer RV electrical PlugIn this video I show how to test a 7 way trailer plug wiring harness for towing a travel trailer or RV by using a...

www.youtube.com

The real issue is to insure that the trailer wires match the trucks wiring

Like White wire on the truck may be the Ground Wire, so you have find the ground wire on the trailer & Tag it White
Then you only have 6 more wires to identify

Then run a continuity tester on each wire

Simple Huh ??

 

[crash68]

If it's just the left rear running light that doesn't work when plugged into the truck, there's a problem with that light and/or the 7-pin plug/jack.
Inspect the 7-pun plug on the truck, even pull the plug from behind the bumper looking for and corrosion. I'd probably replace the trailer 7-pin plug as they're fairly inexpensive.
Being this is a boat trailer I'd replace all the lights with sealed LED versions, you should be able to find them at https://www.etrailer.com/

 

[Rlaf75]

I had a similar problem with my enclosed trailer. I wound up replacing the 7 pin connector on the trailer and had to clean the ground connection on the trailer. Like previously mentioned, they have a circuit tester you can plug into the truck connector to verify that the truck connector has power. Most auto parts store will have them and they will show if the truck is the problem.

 

[62Blazer]

Typically the running light power is just one connector at the 7 pin and then y's off to the left and right side on the trailer. If one side of the trailer works and the other side doesn't it should be something in the trailer wiring. Where did you wire in the 12 v power into the trailer wiring? Easiest way to test is simply take a test light, or volt meter, and start checking for voltages down the circuit and see where you lose power. I will say that the vast majority of trailer light issues I have found are related to bad grounds, especially right at the light. The other question is when you connected the 12 V power what did you do for a ground?