How to Test Trailer Wiring to See if There is Blown Fusible Link Installed Inline

Question:

I have made sure all my grounds are clean, and no wires that I see is cracked.My issue is I am getting power to my marker lights on front half of trailer, but my back ones are not working... they have been replaced and self ground and still do not come on, but at the same time getting power to my back break lights... Stumped!! underneath the trailer are these foam orange little things look like ear plugs with the wires attached to.. are these a fuse or grounds?? older travel trailer, thought the power to marker lights might being stopped at this point no idea. If I am getting power to the back breaks lights should all these marker lights be working... not just the front of trailer??

asked by: Mark

Expert Reply:

Can you probe the wiring on either side of those plugs you mentioned to see if the voltage stops at them? Use a circuit tester like part # PTW2993 to see where the voltage stops on the circuit and you'll know where to track down the problem.

expert reply by: Jameson C