Running Lights Trouble

Amber AND red "running" or marker lights are all on the same circuit and IF there is a fuse on the trailer (most do not have a fuse) it would have to be good in order for the front makers to light up..

Rules out the vehicle AND a fuse on the trailer if the front ambers are working.

You have either a broken ground or broken marker light wire going back to the rear of your trailer.

Since the Stop/Turn lights are working that pretty much rules out a broken ground since the Stop/Turn lights share the ground wire used for the rear markers.

Pull the drivers side rear taillight and verify if you have power on the taillight marker.

No power there most likely a break from the front to back.

You can follow the TV to trailer cord on the tongue, back to the junction box on the trailer. In that junction box if you are lucky the manufacturer may have run the rear marker light wire to that box. Verify that all wires are connected properly.

You could run a temporary marker light wire from the front junction box of the trailer to the drivers rear tail marker and see if you get results (this effectively bypasses the wiring in between front and rear).

If the temporary bypass works then just find a permanent route to run the replacement wire along the underside of the RV.

Marker light wiring tends to be point to point (from marker to marker) making finding bad wiring a real joy sometimes..

If any of the running lights have power, you already tested the truck, no need for a tester. You need to find where the disconnect is, perhaps there is a common ground for the remaining lights.

Run a temporary ground wire from the frame to one of the failed lamps and see if it lights with the ones that work.

Check the ground wire(s) for the red running lights.. If you have power to the fronts, then you are getting power to that at the plug.

agesilaus wrote:
Get one of these and see if your truck is the problem.

Which item are you suggesting? Your link goes to a page of items on Amazon.

Get one of these and see if your truck is the problem. On my TT there are no fuses or breakers on the running lights they are controlled from the truck. I had two blown relays because I unplugged the truck while it was still running. Or so I've been told.

Did you ask this question elsewhere, didn't like my answer there or what?