Troubleshooting Multiple Trailer Lights Malfunctioning with Different Tow Vehicles

Question:

I have both a 2011 Viking Popup Camper and a 2016 MIDI/Shorlandr PWC trailer, and both are having same issue. Ive also hooked up both of these trailer electrical harnesses 7-pin connectors to my 2008 Acura MDX that just had its trailer harness replaced by U-Haul and my friends 2018 Toyota Tacoma truck...and heres what happens: With the vehicles running, Ive plugged in both trailers and I turn on the vehicle hazard lights, and all the trailer lights flash, including the night-time running lights on the sides this is also the result I get when I just have the vehicles right blinker on. The left blinker works normally as it should. Finally, when I push the vehicle brake pedal, I get all the trailer lights on steady, including the night-time side running lights. Lastly, when I turn the vehicle headlights on, I do get all the trailer tail lights and side-running lights as I should. So whats going on with both of these trailers, with the abnormal lights response for brakes, hazards, and right blinker?

asked by: Rob

Expert Reply:

It's a little weird that both your trailers are experiencing the same thing regardless of which vehicle they are connected to, but the best way to narrow everything down is to use a circuit tester # PTW2993 at the back of your vehicles to make sure the pins are sending the correct functions, and then apply 12V power to the various pins on your trailers 7-Ways to check and see how the lights act.

If you're seeing power on multiple pins for your vehicles then it could be that your vehicle socket/connectors are messed up or the wires are crossing somewhere, but if you only see issues when you apply 12V power to your trailer connector then your trailer wiring is messed up on that end and you need to trace all of the wiring for the lights and look for any pinched, damaged, or exposed wring and replace it as necessary.

Attached are some pinouts for vehicle and trailer 7-Way connections for you to reference.

expert reply by: Jon G