Brake lights and turn signals work fine but tail lights do not come on. Same problem with a box trailer I pull from time to time. What should I be looking for on the truck side of things?
You can get a 4 prong tester for a couple $ or as mentioned, just use a volt meter or test light. I've had to replace more than a couple truck end plugs in the past years.
The brown wire is the tail/running lights and runs from the trailer connector to a point where it splits and runs down both sides of the trailer. Think of that wire as a pipe with water running through it. Follow the juice with a voltmeter or test light. When you lose the power you found the problem./
I've run across the same problem with my trailers. In my case, I kept blowing the fuse in the fuse box under the truck's hood. Your truck's owner's manual will tell you which fuses are for your trailer lights.
I later found that I had a bad ground in my truck's trailer plug recepticle. I changed the "outlet" and haven't had any problems since.
This season mine weren't working either. I ended up chasing the wiring and discovered that mice had eaten the insulation off of them. They were shorting against each other and the trailer rail.
