Re: Trailer tailight help.
I troubleshoot by half-stepping the problem. Get one of those trailer light testers from Walmart or somewhere like an automotive store. It looks like a trailer connection without wires and has a set of lights to tell you if your vehicle connections are working. From that test you'll know which direction to look - vehicle wiring or trailer wiring.
Since break lights work, your ground must be intact. That half-steps the problem to the tailight site of things. Blinkers work with brake site of things, so it may be simply a one-wire issue, assuming both lights don't work at the moment. However, don't assume both tailight filaments aren't bad. "Murphy" may be lurking to trip you up with a coincidence.
