I need to tap into the reverse light wire for a my 2016 santa fe in order for my surge brakes on my boat trailer to properly work while I am in reverse. I can only find the circuit in both the hood fuse panel and the actual reverse light compartment located in the hatch. Neither of these places are any good for running a wire back to my tow wiring harness. Does anyone know where I can tap into this wire. Does the wire from the hatch run over to the inside cargo area panel? If so, how do I remove that panel?

 

This question was asked in 2017 but after spending an hour online today looking for an answer to this same questions and coming up empty, I decided to leave a reply for the next person wiring a 5-flat on their 2016 Hyundai Santa Fe Sport. By the way, if you know a better way, please leave another reply because it could really be helpful for someone else. What I did... I opened up the hatch and removed the pop-out panel behind the reverse light. It turns out the red wire is the reverse +12v. In order to get at that wire before the transition to the hatch, I had to disassemble the back portion of the headliner. Pop out the two plastic pins on either side of the light. It helps to have door panel removal tools for this. Then don't pull the headliner down any more because there are hooks under the weatherstripping that are glued to the headliner. Pull the weatherstripping down all along the top and unhook the headliner... then pull the weather stripping down along the driver's side all the way to the bottom. Use a pry tool to pop the side panel out along the driver's side rear so you can run a wire down that side. Back up at the top, disconnect the electrical plugs (there are 2). The red wire continues on in the larger connector. I used a multimeter and checked continuity back to the red wire at the reverse light to make sure I had the correct one. At this point you need to tie into that wire with a new wire that you run down the driver's side of the rear hatch opening. I decided to cut back the loom and shave the wire, and then solder a wire on. I could have used a press-connector but I didn't want to ever have to take it apart again if the connection wasn't good and solder just makes it a sure thing. I used good electrical tape to cover the connection and then more around the entire loom. I failed to find a good way to pass the wire through the body so I ended up drilling a hole behind the driver's side rear pedestal cover where it meets the floor of the cargo area and using a small grommet I fed it through to the area where the trailer wiring adapter is plugged in. From there I ran the wire along with the 4-flat cable of the trailer wiring kit. After that was all done, I used a 4-flat to 5-flat adapter that needs an extra (reverse) wire to work. It was all available on Amazon. Descriptions below... I don't know if links work so I'm leaving those out. I hope this helps someone else.

Tekonsha 118269 4-Flat Tow Harness Wiring Package with Circuit Protected ModuLite HD Module

CURT 57187 4-Way to 5-Way Flat Adapter for Boat Trailer Surge Brakes

Plug up above headliner where I patched into the reverse wire.

reverse wires in the hatch at the back of the reverse light. Red is 12v for reverse

Route for the wire to the base of the rear hatch area.