Electrical cord tester

[Oldman53]

I am looking for a 7 way flat pin tester for the trailer cord. I have one that tests the tow vehicle's receptacle. I need one to test the female connector off the trailer.

 

[Holdmybeer]

You'd need to energize the harness to test for anything other than continuity. If you've got continuity on any one pin then you know the ground is good, if you've got continuity all around and a problem still exists it's not in the harness. In my experience and in keeping with Occam's Razor, solving a trailer harness issue often involved a simple grounding problem.

 

[Wemustrv]

I use a multi meter to check mine.

 

[MemoriesByTheMile]

I use a digital multimeter to test ground (though a marginal ground may not always appear on the DMM as an issue) and I use a long wire attached to the battery positive cable on trailer for testing each pin and checking lights.
If lights all appear to work as intended with wire test I go back and verify ground connection is solid and clean. If questionable I will remove, clean, reattach and use dielectic protective grease. Check ground connections to frame on both tow vehicle and trailer.