Troubleshooting Trailer that Illuminates Trailer and Vehicle Running Lights When Connected

Question:

HI, I started towing our troop trailer for the Boy Scouts. As they say, no good deed goes unpunished. Its and Integrity 7x15 enclosed trailer. The other person who used to tow it also had the same vehicle, GMC Yukon XL. When I plug the 7 plug into the car, the trailer market lights turn on automatically and so do the parking lights on my truck. I have only towed boat trailers, including LCD lighted which this one is and have never seen this before. Also, we do get sway with this, tongue weight is 600, GTR is 7k. We do need to back up with this trailer, it does have electric brakes. What would you recommend for this trailer? Thanks

asked by: Scott

Helpful Expert Reply:

There must be a short on the wiring of the trailer you are towing or on the tow vehicle. Sounds like it has to do with the running lights and the 12 volt power circuit. Since it only happens when the trailer is connected I would expect it to be on the trailer side of the situation.

Check out the 7-way wiring diagram I attached and compare that to how the 7-way of the trailer is wired. You would also need to look for obvious signs of a short like cut or exposed wiring or corrosion.

If you are getting persistent sway with your trailer above a certain speed the solution will be better trailer loading. Try to get the tongue weight of your trailer to be 10-15 percent of the total trailer weight and the sway will stop. Otherwise the problem is worn suspension components or tire that need proper inflation.

expert reply by: Jameson C