Seat Heater Install Rostra 250-1870-TOY

Truck is a 2021 SR5, install should be roughly the same for any year. Big thanks to @RainMan_PNW for helping me understand the wiring.

A few preface notes; the way I did power/ground is overkill, some of the supplies etc. below are optional only if you're doing similar method to mine. I did it for ease of access and future accessory expandability. You end up losing ~3" of center console vertical space. The seats and covers are easy to remove. Getting the covers back on to factory fit was a challenge that I ultimately gave up on and had an auto-upholsterer do. As with any wire routing, the more trim you remove the easier it gets. Take pics as you go of where connectors clip in, where screws go etc. I pre-wired for the rear seats as well, plan on installing the heating pads when it warms up. Some of the videos below are not mine, all credit to the creators.

I purchased the Rostra 250-1870-TOY seat heater kits here for $106 per seat:
https://www.mnrelectronics.com/250-1870-toy-seat-heater-toyota-vehicles-w-custom-switch/
Shipping was free UPS, order was fulfilled in a timely manner, great electronics shop. These are more expensive than your standard seat heater kit, but they include factory appearance switches, pre-loomed wires etc. which was worth it for me.

I/you probably have a lot of this stuff below on hand already.

Other tools/supplies include:
adhesive lined heat shrink:

$14 ELECFUN Waterproof Heat Shrink Tubing Kit 365 pcs, 3:1 Dual Wall Tube - Adhesive Lined Heatshrink for Wires - Marine Grade and Industrial Shrinkable Wiring Wrap Fully Insulation Black/Red, 7 Sizes

https://www.amazon.com/dp/B08SQHH9NS
hog rings/hog ring pliers if reinstalling covers yourself:

$12 Hog Ring Pliers Kit with 270 Pcs 3/4" 1/2" 3/8" Galvanized Steel Hog Rings,Hog Ring Pliers Kit for Auto Upholstery and Fencing,Bagging,DIYCraft,Furniture

https://www.amazon.com/dp/B0CWVDM5JS
cutters for hog rings (I found mini bolt cutters worked): solder iron kit:

$10 Soldering Iron Kit, 80W 110V LCD Digital Solder Iron Pen with Ceramic Heater, Portable Welding Tools with 5pcs Tips, Stand, Solders Wire, Sponge, Paste, for Metal,Electric Repairs, DIY

https://www.amazon.com/dp/B08R3515SF
wire stripper (Klein ftw):

$21 Klein Tools 1019 Klein Kurve Wire Stripper / Crimper / Cutter for B and IDC Connectors, Terminals, More

https://www.amazon.com/dp/B07GFYBW4V
crimpers (can use wire strippers, I prefer these ratcheting ones from HF): wire connectors/terminals (this kits good to have on hand): add-a-circuits (2 max):

$15 BioFuse 12 AWG Low Profile Mini ATT Quick TAP KIT: 2 Add-A-Circuit Car Fuse Tap Adapters, 2 Each (10A 20A) LP-Mini Blade Fuses, 4 Zip Ties + Fuse Puller

https://www.amazon.com/dp/B08QV8Q3BW
zip ties: Tesa tape:

$7 tesa 51036 High-Performance PET Cloth Automotive Wire Harness Tape, Black, 19mm x 25m, 1 Roll

https://www.amazon.com/dp/B016ZMXLEI

Optional:
HDPE/ABS for interior/engine fuse panels:

$33 HDPE (High Density Polyethylene) Plastic Sheet 1/4" x 36" X 24" Black Light Texture Both Sides

https://www.amazon.com/dp/B07F7G83CK
~18 gauge wire (~8 feet to extend accessory power, ~2 feet to extend illumination power): https://a.co/d/0gbgss9
8 gauge power and ground wire, lugs/ring terminals:

$38 Taukealugs AWG 8 Gauge UL1015 Battery Power Tinned Oxygen Free Copper OFC Welding Cable Wire Red Black-Total 20FT and Lugs Terminal Connectors with Heat Shrink Tube

https://www.amazon.com/dp/B0BZVFX4DQ
m6 rivnuts and tool (Have the Astro Pneumatic one, HF one looks the same): m6 x 60mm bolts (I used 4 bought at hardware store):

$7 binifiMux 10pcs M6 x 60mm Rivet Countersunk Socket Cap Bolts Screws Connecting 304 Stainless Steel

https://www.amazon.com/dp/B08RJDGS7X
fused power distribution block:

$18 WUPP 12 Volt Fuse Block, Waterproof Boat Fuse Panel with LED Warning Indicator Damp-Proof Cover, 6 Circuits with Negative Bus Fuse Box for Car Marine RV Truck DC 12-24V

https://www.amazon.com/dp/B07GBV2MHN
wire lug hammer crimper:

$19 TEMCo Hammer Lug Crimper Tool - Crimps 8 AWG to 4/0 Battery & Welding Cables (Workbench-Mountable)

https://www.amazon.com/dp/B00E1UUVT0
Rubber feet for fuse panel:

$10 4 Large Extra Tall #2-1" H X 1.10" W Round Rubber Feet Bumpers -Made in USA- Heavy Duty/Non Marking for Furniture, Tables, Chairs, Desks, Benches, Sofas, Chests. RoHS & Reach Ready/BPA/Prop 65 Free

https://www.amazon.com/dp/B01LDT7UHM?ref=ppx_yo2ov_dt_b_fed_asin_title

1) Disconnect your battery negative, wait a few mins (supposedly takes a few mins for the airbag system to de-power, not sure it true but aired on the side of caution). Remove the plastic covers over the back seat bolts. Reach under the seat with needle nose pliers to pinch the metal retainer clips and pull the plastic covers straight back. Undo the 4 seat floor bolts and connectors under each seat. Remove the seats from the truck. This video does a great job showing the whole seat removal, trim, cover etc. for the driver seat, process is about the same for passenger side.
https://www.youtube.com/watch?v=cwmjuVwXYvU

2) The heating pads require some trimming and I was a little confused at first because the way you have to trim them to work (at least in my 2021 seats) sort of contradicts the instructions. Their video instructions say to lay them out flat and mark the center of the listing(learned that's the term for the valleys in the seat foam), and then cut windows, which doesn't work. The paper instructions say to lay the heating pads out and fold them into the listing to trace windows, but that the heating pads shouldn't be folded into the listing. Without folding them into the listing they won't fit. I did sort of both, I folded the pads into the listing, marked where the hog rings attach, and then cut a "max 7/8"" wide window that goes from the inner edges of the adhesive on both sides. The tricky bit is that to make the pads fit, and to be able to reattach your hog rings, you have to have the adhesive part folded into the listing.

The seat bottoms with covers removed from a top down perspective look like this:

The red lines are where the listing is. Embedded in the seat foam in the listing valleys are little wooden dowels, and then on the seat cover there are metal rods that run more or less the length of the red lines above. The seat heating pads are narrower than the vertical listing, but wider than the heating pads, which means you have to put the listing rods over top of the heating pads. The inner rectangles above are the "windows" you have to cut out so that the listing rods can attach to the listing dowels. If DIY'ing, I'd try not to detach the velcro at the front corners of the seat. I put one of my covers back on and I'd say it looked ~85% as good as before I took it off after a lot of trial and error with the hog rings, but I ended up taking my seats to a local auto upholsterer to have him put the covers back on to get them factory snug. He charged me $80 per seat to put the covers back on.

From a 3/4 perspective to try and illustrate how the pads have to fold down into the listing valleys, the heating pads look sort of like this:



The yellow lines are the adhesive strips along the edges of the heating pads, the dashed lines are the "windows" you have to cut out, red lines are the listing dowels, green x's hog ring attachment points like above (not showing the vertical listing/hog rings). Kind of hard to illustrate how the listing rods are wider than the windows you cut out/they're more or less the same width as the heating pads.

After you trim and take care of the pads, lay them down, get them straight, mark your edges, and mark where the thermostat sits, it should be 1-2" from the seat back and not wedged into where the seat bottom/back meet. Once you've got the layout marked on your seat foam, peel back the adhesive and start pressing them down, I worked front to back. It's easier to fold them into the listing if you spread it apart with one hand and press the heating pads in with the other.

3) Reinstall your covers using hog rings/pliers, or take them to a shop. Installing the heating pads isn't bad/hard, the covers kept bunching/wrinkling at certain parts and after a few tries I gave up, a more determined/skilled/less perfectionist person could for sure do it, two people would make it a lot easier.

4) With the heating pads installed and covers back on, I loomed the wires coming from the pads, routed them under the seat, and zip tied them so that the main connector is near the other connectors under the seat.

5) Installing the switches. I had 2 open slots on my panel under the AC controls. One switch fit perfectly, the other I had to notch a little bit of plastic circled below for it to fit correctly

Switches installed look like this:


Remove the shifter area trim as well and set aside.

6) This next whole part is optional. If you want an easily accessible interior accessory fuse panel, this is a good option imo. If you just want to do the seats, you can bundle all the wires/relays and find somewhere in the dash to secure them. Remove the center console, 4 bolts inside under the carpet, 2 screws attach it to shifter column trim area. Run your 8 gauge power from battery, through driver side grommet, and route to center console area. Plenty of videos on Youtube for this. I used some scrap HDPE to remake my fuse holder panel in the engine bay, 4x6" panel to mount both my fuse holders to (larger wire is for audio system).


7) Take the carpet out of the center console, trace it onto your HDPE, and cut two panels of the same size. Measure/mark where the center console bottom bolts go, and then drill 9mm holes on the 4 corners of your two HDPE panels sandwiched together so the holes line up. Insert m6 rivnuts into the 4 corner holes on one panel. Lay your "bottom" panel with rivunts into the center console. Use a step bit to drill out ~1" holes through the HDPE panel and bottom of your center console to pass wires through in front (and back only if doing rear heated seats too). Mount your fuse panel, and relays to the panel. Route you wires, secure everything. Should end up looking something like this from the top:


You can see the 4 rivnuts on the corners that match up to where the center console as valleys where teh factory bolts go. I was lazy and didn't depin/shorten anything, so I ended up with weird slack underneath that I secured. I added rubber feet to keep the panel up off the bottom of the center console but if you trim the wires to length you wouldn't need to. Bottom side:


8) From here, it's just routing your wires and making connections. On the panel above, my power comes in at the top of the panel, ground comes in at the bottom. The front seat wiring comes in on top, as well as the accessory circuit wires and the illumination wires. On the kit instructions, it's kind of confusing on which wire is which. The big red fused wire is your +12v power, the yellow wire is your illumination, the small red wire is the accessory wire, and black is ground. I routed the front seat switch plugs to the AC area along with the illumination wires. Continuing on from there I routed the accessory circuit wires along my power wire back to the interior fuse panel area. For illumination, I de-pinned and cut wire #5 on the flat black 8-pin connector after testing for illumination. @RainMan_PNW confirmed this is the illumination wire for the parking sonar switch which I don't have. If you do, you could instead t-tap this wire. I soldered all my switch illumination wires to it:


I routed the ground wire out the back of the panel, to the factory amp ground point under the passenger seat here:


I routed the connectors for the seat heaters under the carpet, coiled up the slack, and left enough sticking out from under the carpet to match the length of the existing factory wiring.
Reinstall the center console, pull your power/ground up through it/your panel, bolt the center console back down using the factory 10mm bolts, trim the wires to length, crimp your lugs on (lug crimpers work easier than a hammer crimper for this), and attach your power/ground to the panel. Some more pics:


I put some adhesive foam around the edge to stop rattling.


Install your "top" panel using the 4 M6 60mm bolts:

and then reinstall the carpet piece over top of everything. You've essentially got a false floor/switch panel sandwich.

EDIT: I realized in retesting things that the Cig. No 2 circuit is constant. Connecting the accessory wires to this circuit drained my battery. I ended up using a test light to re-check things and found a couple empty ignition fuse slots.


Be sure to orient your add-a-circuit correctly, on my truck the "hot"/line sides are like this:


All in all they turned out great and they get super hot super quick. Highly recommend, and like I mentioned before if you're just doing the front seats or just seats in general and don't want an accessory fuse panel, you could install these by just tapping factory wiring and tucking the relays up into the dash somewhere. I'm probably forgetting stuff. Happy to answer any questions about any of the above steps.

 

Great write up!

 

Thanks! I tucked the rear wiring up into the back of the center console, found out that whole part comes off easily with clips. The switch panel I ordered from you should be here tomorrow, I’ll update with pics of it/the rear heater switches installed.