Boat Trailer Turn Signals Both Blink When Connected to a 2012 Hyundai Elantra Touring

Question:

Hi there, Im stumped and I hope you can help me out. I installed a tbox/adapter to my 2012 Hyundai Elantra Touring and followed the instructions to the letter, even tested every wire I used signals, lights and brake, and then connected it to my boat trailer which has new lights and harness. What is happening is odd... The connector from the car has green LED indicator lights to show what is on etc... When not connected to the trailer, everything works fine eg. Left signal on, only LT LED blinks and so forth. When I connect my trailer, the signals only work at the same time. If I put on the righ or left alone, both go at the same time. Brake lights dont work at all. Also, the LEDs indicate the malfunction that is to say that once connected to the trailer, Ill turn on my right signal, for example, and both right and left LEDs are on, which is what is happening on my trailer. My grounds are perfect. My instinct tells me its got to do with what I did in the car, but I would have no clue what to change since it the LEDs and instructions seem good. Your advice would be greatly appreciated. Cheers

asked by: Alec

Expert Reply:

If the 4-Way is working when the trailer is not connected but you have trouble with the lights once the trailer is connected, to me it sounds like an issue on the trailer. To double check the vehicle though you can follow the help article I have linked for you.

Nine times out of ten problems with trailer lights are either related to the ground or a dirty or corroded connection somewhere.

The first step is to make sure the trailer connector is clean and free of corrosion. Then make sure that the main trailer connector ground is attached to a clean and corrosion free bare metal surface. The lights, too, should be grounded to clean and corrosion free bare metal surfaces.

Some things can interrupt a ground. For example if a plastic license plate holder was placed between a light ground and the trailer frame that can cause ground problems. If the trailer has an aluminum frame, tilt bed, or folding tongue, any of these things can interrupt the ground. Running jumper wires from the trailer light grounds to the main trailer connector ground can help.

Some of the trailer wiring harnesses for your 2012 Hyundai Elantra do not work well with LED lights. The Curt trailer wiring harness # C56175 for example is not recommended for vehicles with LED lights. For a compatible hardwire harness I recommend # 119178KIT. And for a plug-in style T-connector harness I recommend # 118473.