Here is a copy and paste from my contribution on the aftermarket seat heater thread found here
http://www.toyota-4runner.org/5th-gen-t4rs/80123-seat-heater-install.html
From the seat heater installation of the Amazon kit from earlier in this thread.
If you are considering wiring this kit in the same manner I did, you NEED the manual offered in this forum by Nashman69, or another factory reference manual.
Everything I did was based on the Seat Heater (2010 4runner) .pdf from Nashman69 (He’s getting some beer money from me :cheers

.
You, of course, have a multi-meter and know how to use the continuity function because you should verify that the connectors and the wiring that goes to them is what and where it is supposed to be BEFORE you cut anything, right? :director:
I used the factory 20 amp (S/HTR FS position 13) of the CJB (interior fuse box) for both passenger and driver sides. Mine had a fuse already installed and no action was required to have, verified by testing, output pins controlled by this fuse (for testing purposes the connector side of the fuse insert was towards driver side fender, battery side towards the passenger fender). I used the outputs at the front and back of the CJB.
Passenger side is located on the back, towards the firewall, of connector 2C pin 14. It's the bottom, blue, wire in this picture taken looking up from the brake pedal towards the dash.
I used a mirror to verify I was hitting the right pin/wire when testing for continuity.
Driver side is located on the front, towards the cabin, of connector 2F pin 5. Mine was an empty hole originally. Here it is after adding the pin and white pigtail in position 5 and labeled with masking tape.
Our 2012 SR5 had the seat heater wiring from the fuse complete to the passenger seat connector Na1 pin 6, blue wire being hit with test lead from other side in this picture.
The passenger seat side of the connector had nothing attaching to this pin.
I released the pin from Na1 pin 6 and ran a wire from here back to the center console where I mounted the kit relay (actually just next to the console, under the carpet, and just aft of the inner seat mount points.
The driver side lacked wiring from the fuse onward. I considered using the passenger side to power both seat warmers but after testing the resistance I opted not to.
So, I ordered the correct pin with pigtail (Toyota part # 82998-24530)
to use at connector 2F pin 5 and ran new wire from this to under the seat. It's highway robbery at about $14 but time was critical for me so I grabbed my ankles. They can be bought without the leads for about 29 cents each here:
Ballenger Motorsports ? High Performance Electronics
I tied in the kit relays to these 12V ACC power wires, and used a common ground for both under the center console (in this case a bolt holding down the transfer case shift lever lower boot after testing for a good ground).
For the kit switches I ran wire from the illumination and ACC power wire from the stereo connection (I already had this exposed doing a new headunit) but otherwise I would have used the before mentioned shift lever position light and some ACC power to tap into.
As others have mentioned I also found the green illumination to be intrusive. So, I opened up the switches and modified them.
There are two lights and the green one is disproportionately large compared to the yellow (where the yellow piece is to the right along the green plastic inside the light housing).
Without getting all technical about what this is made of, here is what I did:
Using a black sharpie I covered inside of the switch corresponding to the green LED area with ink.
I covered, reassembled, and tested several times before ending up with about 85% of the light I wanted eliminated.
I then added a small piece of gorilla tape cut to fit exactly in the area behind the sloped “green indicator” area of the switch.
The horizontal bar indicator still lights and there is just enough spill from the dial to be able to make out the position in the dark.
A warning about the pins in the CJB: The wire they connect to had some tension in my vehicle and the barbs holding the pins in are VERY tricky to release. Figure out routing before slipping these in.
You may have to separate connectors 2C or 2F (they are two separate connectors slid together) before installing new leads. If removing them you MUST separate them and release the barb tension (not easy).
Also, I would download the manual from Nashman69 and stare at the seat heater diagram until you have a conception of the factory system.
.
Overall I am very satisfied.
I could return to stock relatively quickly. I can also keep my fuse cover attached. This was a big deal to me with a messy dog and wife.
Hope this helps. I'll try to answer any questions here.
MOJoWales