Troubleshooting 7-Way Wiring and Trailer Brake Installation

Question:

Hi, I just converted my trailer to 7-pin with brakes from 4-pin. Last night I finished and hooked up the trailer to my brand new 2017 Ram 1500 and everything worked beautifully, so today my plan was to run to an empty parking lot to allow the self-adjusting brakes to get adjusted properly and now nothing works. No lights, no brakes, nothing. I re-did the ground wire and still nothing. The only thing that I could think to be wrong with the wiring is perhaps a bad connection on one of the wires to the trailer brake itself. Is it possible that one connection at the brake would shut down everything?

asked by: Josh

Expert Reply:

Your newly-added trailer brakes use a totally separate circuit than the lights on your trailer. But I agree that a bad trailer ground would have been my first suspicion too. Make sure your main trailer ground is made to a clean bare metal spot on the frame, one free of paint, primer, rust, grease etc.

I suggest you test the vehicle and trailer separately since this will isolate the issue to either the Ram wiring or the trailer.

Disconnect the trailer and apply power to each of its circuits on the 7-way plug, one at a time, to see if any of the light circuits or brakes operate. You can use the battery in the truck (or a well-charged spare of you have one around) to apply direct 12V power to each lighting circuit. Connect the battery ground to the 7-way plug's ground contact and the positive to the brake circuit (see linked photo, please). You should be able to hear the brakes hum as the magnets energize. Repeat the test on the lighting circuits. If the trailer functions still do not work then you'll have to trace your wiring from end to end.

If they do work when directly powered then you know to go to the truck. Use a tester like # PTW2993 on each circuit of the 7-way while a helper activates each light function (and the manual override on the brake controller) so you can test the 7-way socket for the signals that should be there on the various contacts. If you find light and brake signals are not present on the 7-way the you know to check fuses on the truck and its wiring harness.

You can refer to the linked article for more troubleshooting help.

expert reply by: Adam R