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.

 

[RBryce]

I could not find one anywhere so I built one. Bought a harness pigtail that you would wire into the truck. I joined all the leads for the lights (tail lights, brake lights and the tag light), tie in the wire that goes to the fuse panel, put alligator clips on the bundle and on the negative lead. If connected to shore power, disconnect it. Plug the harness into your trailer, take your battery off line and connect the clips onto the trailers battery. All exterior lights should come on, as well as interior lights. Just don't connect the blue wire unless you want to test the brakes as well.. Once the harness is built, all you need to do is plug it into the trailer, open the battery isolation switch, connect the leads and look.