Thunderslide

It could be the ground to the light as well. a test light should make quicker work of finding the problem.

kind of Ironic but I can read red but I am mostly color blind.

SD F150

To confuse this situation more, the yellow marker lights on a trailer only have one wire that come out of them. As stated, they tap into the wiring to the red tail lights, which in my case are working fine. Guess there is a glitch in the wiring somewhere. Gotta take a look.

ford4wd08

that mean the yellow lights ground themselves threw the mount on the trailer, like a screw into the trialer or something....

Thunderslide

That just means that they are relying on the mounting screw to make a ground. If you don't have one get a 12v test light from a parts house or hardware store. I would bet money you have power to the light but a bad ground. Did you change the housing or just the bulb? I don't know how much you know so don't take this personally. for the light to work the power must pass through the bulb and back to the trailer. The result of this action is to make the light glow because of resistance, just like a toaster glows orange. the light is brighter because it is in a vacuum and that makes it not fail. so if the power gets to the bulb but not back to the trailer the light will not glow because the electricity it not passing through the bulb it exactly what happens when you turn a switch off. you "open" the circuit.

SD F150

I am not offended, I came here for help. I don't know much, just general stuff. The more I think about it, it must be the screw as a ground. I have always had trouble with that system in other lights, where there was not a dedicated ground wire. I'll check it, thanks.

SD F150

This is confusing....

Back of the marker light, there is no place to screw this thing onto the trailer.



It is held on by this guard, which just goes over the light, but it does not provide ground.



I emailed the company with part #, and got this response.



Back to the drawing board!

Thunderslide

pop the yellow lens off and provide picture. with the picture you showed... Bad ground without question!!!!

SD F150

Ok to complete this thread, and show how little I know....

Here is the cover popped off, you can see on the right, there is the ground, and this is where you mount to the trailer frame.



I assumed the guard held the light on....

Thanks for everyone's replies, this is the first time I have had to install marker lights, now I know where to look!