Called Hitch House. They are installing the Curt hitch and directly wiring a 7-blade harness made by Curt for the SC, which “matches” the one for the Telluride, along with a brake controller. It’s all in stock so they’re doing it tomorrow. They did a SC last week here in Edmonton, Alberta (Canada, eh?), so the tech must know what he’s doing. Total cost is way less than Hyundai quoted me for the hitch and 4-way.
What is the part number of this mysterious Plug&Play Curt product you/they speak of? Curt's website only shows a 4-PIN Plug&Play for the Telluride (#56420); which happens to be the same part number I used for my 4-PIN light bar.
They confirmed that this business of adding a 7-way adapter to a 4-way harness won’t work with a brake controller. Which seemed odd to me from the beginning. And JMII you are spot on about the dealers not having a clue.
As posted earlier...
You want the factory 7 pin because then you can use the brake controller wiring under the dash:
The Official Santa Cruz Towing Thread
However if you are going with the wireless brake controller then it doesn't matter... just go with the 4 pin and adapters as needed.
^ THIS ^
The 4-PIN to 7-PIN/BLADE (being used interchangeably - a PIN is round and a BLADE is flat) should work fine with a "wireless" brake controller as JMII stated earlier.
I will be using the Curt 4-PIN to Dual-Function 4-PIN & 7-PIN/BLADE adapter; most likely with a wireless controller. The reason I'm going this route is I need the 4-PIN plug to run my light bar and the 7-PIN/BLADE to plug in the trailer. If the trailer I'm towing is a 4-PIN, then I will simply plug the Curt 7-PIN/BLADE to 4-PIN posted earlier that has the backup beeper built into it (arrives tomorrow).
The end result will give all of these abilities:
1) Light bar and backup beeper for everyday driving while not towing.
2) Light bar, backup beeper and 4-PIN towing ability.
3) Light bar and 7-PIN/BLADE towing with wireless brake controller, no backup beeper (removed).
Hopefully that clears up any confusion.
I'm skeptical of your installers' claims that the Curt 57672 Dual-Output can't be hard wired into the under dash Hyundai system, but that's certainly not the easy way to do your installation.
Please get the Curt 7-Blade Plug&Play part number for the rest of us here. That will solve the problem of Hyundai dragging their feet on getting that to their dealers for every to purchase. Thanks!