Heated seats

Hey guys, finally got a day free enough to install heated seats in my 2017. All in it only took about $100 in parts, 4-5 hours' time, and they work fantastic. This is the third Toyota vehicle I've installed these on (dads 14 Tacoma and girlfriends 2020 4runner) and my tundra was either the trickiest of the 3 or I was the most impatient this time lol. Either way they're installed and just intime for those 20-degree mornings. Also, HUGE shoutout to rainman_pnw for the awesome 3d printed switch panel trim piece. if you haven't checked his stuff out, you should.

PS... I was dumb and forgot to take pictures of the install along the way so I can't really post an instruction page. But if enough people are interested, I can go back and "reinstall" on one of the seats and get photos along the way to post a how to. Overall, it's not a hard install just an annoying one. If you have very basic electrical knowledge, you can do it.

One last thing if you plan on doing this and have seat covers like I do, it takes significantly longer to heat up. my truck with cloth seats and seat covers it takes about 4-5 minutes to actually feel the heat on high. My girlfriends 4runner with just cloth seats and same seat heater kit it takes right around 1-2 minutes on high.

Let me know what y'all think.

 

I'm in the process of stripping my seats, have one torn down and the pads on, need to pull the drivers seat and repeat. Did you use an add-a-circuit for power and if so, which circuit did you tap?

 

I did, here's the link to the one I bought.

$6 Mini Blade Fuse Holder Fuse with 10A, 20A Fuse - Tap 12V Car Add-a-Circuit Fuse TAP Adapter with Mini Blade Fuse （2 Sets）

Amazon.com: Mini Blade Fuse Holder Fuse with 10A, 20A Fuse - Tap 12V Car Add-a-Circuit Fuse TAP Adapter with Mini Blade Fuse （2 Sets） : Automotive You might be able to find them at AutoZone or somewhere similar if you don't want to wait for shipping. I would just make sure you get one that can handle a 20amp draw. If I remember correctly each seat should draw 9 amps a piece at full power. Also, Toyota uses the same fuse block for most models (not sure about the SR) so your truck should already have a fuse slot for seat heaters you can tap into, and it recommends a 20amp fuse as well. Lastly Make sure you plug the tap into the existing seat heater location if you want them to turn on and off with the ignition. Otherwise, they will stay on even when your truck is turned off.

 

Sweet thanks. I seem to have misplaced my fuse panel cover when doing some audio. I was looking at my panel and I don't see a 20 amp in that slot and it looks like they must have redone the fuse panel after August 2017 production. Looking at the Ultimate Wiring Diagrams thread and I found this:

which matches what you've got there, but for post August 2017 I just found this:

which makes it a big ol PITA since IG NO.5 is in one of the engine fuse panels

Rather than running another wire through the firewall grommets, I wonder if anyone has used/knows if any of the blank slots on the interior panel are keyed? I can always go out with a test light and try them and I'll probably have to and hopefully find one. I've got the Rostra Toyota heated seats and am assuming they're about the same draw at full tilt as any other seat heaters and using your 9 amp per seat as reference, the only other two circuits with a 20 amp I see that i think would be keyed are: (I know so long as you orient your add a circuit correctly it's independent of the original circuit, but you'd want an original circuit of sufficient amperage/wire gauge to support another circuit right?)


which are located here on the interior fuse panel:

 

Sorry for the late response.

I know when I did my dad's Tacoma, I used the fuse slot for his r/l power window BUT he has an access cab and doesn't have windows that open there anyway so it was an empty circuit. I'm not sure if you added the fuse tap to one of those slots, if you would lose those functions or if both the seat heater and the power windows would work. If they both worked, I'm not sure you'd want to have both of the heaters on high and use the window at the same time, will probably pop the fuse. However, I have seen where it is doable to add power to an empty slot in the fuse box in which you can splice the ignition wire and have it only run when the key is turned on. It will still probably warrant running a wire through the firewall though which is what you were trying to avoid.

 

If you orient the add-a-circuit the correct way as far as line/load go, the newly added circuit should function independent of the tapped circuit, but I've never thought about how that would affect the home run or feed wire going into the panel, i.e. if you have a 10 amp circuit, and add another 10 amp circuit to is using an add a fuse, wouldn't that have the potential to draw 20 amps on the feed wire and possibly burn it up? I guess I'm not knowledgeable enough to know what gauge the feed wires going into the panel are but I guess I assume they use different gauges of wire for say a 5 amp vs 25 amp circuit. If I were able to determine that one of the empty slots is hot, I could use that for the my heaters red +12v constant wires (which have an inline fuse preinstalled with a 7.5 amp fuse), I'd just have to make sure that empty slot can support a 15 amp circuit (don't know how I'd determine that wire gauge beyond looking at it). My heaters have a yellow wire that calls to be wired to the Headlight/Night Lamp (dimmer) +12 volts - 5 amp circuit, which I think just translates to any keyed/ignition circuit.

@RainMan_PNW seems to be the electronics guru, maybe I can get him to chime in and advise.

 

Crude illustration of a fuse socket


Crude illustration of that fuse socket with a fuse tap


The fuse tap is seated into the original fuse socket, and the LOWER socket in the fuse tap basically acts as an extended version of the original socket (passing the power from the source to the load). The UPPER socket in the fuse tap is extending (tapping) the source and routing it to a new load. You are not adding any load to the original fuse or circuit downstream of that fuse.

You ARE, however, adding load to the source wiring, so you do need to be sure the sizing of that source wiring is sufficient for the additional load you are putting on it. Under most circumstances, the internal wiring feeding the fuse box is sufficiently sized to be able to handle it, but for large loads it isn't a bad idea to use (tap or directly if you can find an output wire) an empty slot. I would also take a look at the EWD for "Power Source" to see the distribution of power as a whole to see where the wiring comes from that breaks out to different circuits.

yes - basically this. For the most part, the wiring should be fine for most of the kinds of things you are adding, but it doesn't hurt to chase back to one of the connectors coming into to internal fuse box to see what that wire size is for that "cluster" of fuses.

For fuse taps, I would recommend these - they fit more compact and the use the same fuses as OEM.

$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

Where did you find that fuse box diagram? That's sweet.

I would trace the seat heater diagram in your truck - I wouldn't be surprised if a lot of the wiring is already there coming from the IG NO.5 relay.


The PA1 junction connector is up near the firewall grommet. Look for a gray wire in pin #9 on the yellow harness side of the below image.


And PZ1 is under the driver's seat. Look for a gray wire in pin #6 on the yellow harness side of the below image.

 

Do you have a link to the seat heaters?

 

I bought my kit on ebay and the seller i bought them from is currently out of stock so i cannot link it. But if you get on ebay and search "Tundra seat heater kit" there will be a ton of options and switch styles. Just make sure when you are buying a kit that the heater pads themselves either have perforations or a break in the heating elements (so you can cut out where needed), as shown below, otherwise you will not be able to hog ring the seat fabric back to the seat pad/foam. The connection points between the fabric and the actual seat pd/foam are at the seams in your fabric for reference.

 

So, it sounds like per Rainman's response below you could potentially tap into a fuse slot already allocated to another function BUT to make sure the feeder wire is large enough to be able to support both functions in congruence. you would also want to make sure it is a keyed connection, so they don't stay on when the truck is off. From looking at generic wire size/draw charts online if the feeder cable is 16ga or larger you should be able to support up to 30 amps for up to a 7' run but I'm no electrician so you may want to research yourself and make that call. I used 14ga for mine but mainly because I had a bunch left over from recently rewiring my boat.

 

@RainMan_PNW the link below has all the main and cabin fuse boxes for Tundra's from 2001-2022
https://www.startmycar.com/us/toyota/tundra/info/fusebox

 

I'm not sure which ones OP has, but I've got the Rostra 250-1870-TOY ones, $106 per seat, purchased through this retailer: 250-1870-TOY Seat Heater Toyota Vehicles w/ Custom Switch - M&R Electronics Inc. These have OEM-style switches that fit the blanks by the usb outlets/cigarette lighter.

They do require some trimming of the pads 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. Planning to do a full write up once I'm done/figure out the best way to wire and upload a bunch of pics I took.

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.

 

I was able to grab a pic of what I believe is the PZ1 connector under the seat (didn't look for PA1 yet cause it's too damn cold here lol), but would this be the correct gray wire? Pic is from the back, but pins are numbered from left to right, top to bottom if you're looking head on at the connector correct? In which case the pins would be numbered like so:


and that would be the grey wire coming from the Ig No. 5 relay in the corresponding engine fuse panel?

I also just noticed in the install directions that it says:

A. Red/Yellow Wire - Connect to accessory +12 volts circuit. (Note: Improper installation could lead to battery drain if connected to a constant battery source.)
B. Red Wire - Connect to +12 volt constant circuit.
C. Yellow Wire - Connect headlight/night lamp (dimmer) + 12 volts - 5 amp circuit
D. Black wire - It is recommended to connect the ring terminal to the vehicle body using an existing common ground point. If one is not accessible, connect to a ground wire with a high current capacity.

On the wiring harness for the seat heaters, I've got a black wire (ground, easy), a red wire (constant +12v) and then another red wire and a yellow wire twisted together. I guess I'm confused as to why the directions list both a Yellow/Red wire and a Yellow wire, guessing it's just redundant wording? If the grey wire above is indeed the one coming from the Ig No. 5 circuit, would that be suitable for connection to the Red/Yellow wires that come pre-twisted together? And then from there, it's just finding a constant +12v circuit in the interior fuse panel that can support a 15 amp circuit (7.5 amp fuses come pre-installed on the inline fuses).

Sorry for all the questions/confusion, just want to make sure I've got my bases covered so I don't burn up any wiring.

 

You do a much better job of explaining than i do. and the graphics are spot on. The way i got around the metal rods being too wide for the hole you had to cut in the pad was to lay the pad flat over the trench in the seat pull the upholstery down through the hole in the heater and insert the rod from underneath, then hog ring it. It was tricky but easily doable just kind of have to force it. You may have to cut a little bit of the pocket that the metal rod sits in.

 

I attempted this at first but gave up/didn't cut the pocket that the metal rod sits in lol, good to know that's an option and worked out because it's probably a better idea than the way I did it with the heating pads folded down into the seats. I saw another post somewhere where a guy just cut little squares in the heating pad big enough the put the hog rings through, and he had his pads folded down into the seats so I figured it must be somewhat okay although not as good/ideal as the method you described. Hopefully I didn't ruin them in doing so.

 

I need to take some time tomorrow and digest this, then respond

 

Not sure if it’s any help but thought I’d drop a pic of the wiring laid out:



From left to right: Red +12v constant, pretwisted red/yellow +12v accessory (I think), black ground, switch, relay ?, plug for heating pad. I’ve got tomorrow off and will use a test light to figure out if any of the blank slots have constant or ignition power and if so, attempt to trace the EWD to figure out where the feed wire for those slots comes from and if it can support a 15 amp circuit for +12v constant as well as a 10 amp ignition circuit for the yellow wires (5 amps per heater). With the length of the red, red/yellow, and black wires they won’t reach under the seats for that potential +12v grey wire without adding length or finding that wire up near the PA1 connector. Also been mulling over just running another power wire through the firewall to a bus bar for future accessories like a dash cam I’ve been meaning to install and eventually heated seats for the rear.

 

Sorry for the multiple posts, “thinking out loud” here, the cigarette lighter no. 2 fuse is on the interior panel, 15 amps, should be ignition, and assuming that’s the cig lighter in the center console yeah? In which case I’ll likely never use that/could safely make that the 10 amp (5 amp each heater) ignition/accessory circuit, and then it’s just a matter of figuring out either running a new power wire/bus bar or testing the empty slots for constant power and seeing if the feed wires good to support 15 amps in one of those empty slots.

 

Got it. Still need to read a bit deeper, but here’s the wire functions:
Red (BAT) with fuse - power to the actual heating element, which runs to the relay.
Red/yellow (ACC) (Thinner wire wrapped with yellow) - this is the power to the switch that then goes to the coil in the relay because the switch can’t handle more than a 3A direct load.
Yellow (ILL) - this is the backlight for the switch
Black (GND) - duh. Grounds a bunch of things - the switch backlight, the relay coil, the actual seat heater.

crude diagram - red/yellow is orange in my sketch, and yellow is dark yellow.

 

You don’t want the yellow and the ”red/yellow” on the same circuit… one (R/Y) is powering the relay coil to activate the actual power to the heater, and the other is the backlight illumination (best thing there is to slave off the ILL+ wire from another switch).

The R/Y is never going to see more than 1A TOTAL for both heaters in reality (standard 12V mini auto relays like that are rated around 0.2A load when on), so you are fine tapping any ACC circuit and putting in their 5A fuse (or one of your own).

The Y is also miniscule load - not really something I would even worry about separate fusing myself.

The R (BAT) is the one that you will want to run a dedicated 20A fuse for (10A inline fuse per seat)…either directly off the battery or via a fuse tap is up to you.

 

Got it thanks this makes a ton more sense now. I was foolishly thinking that the Red/Yellow wire we're supposed to be wired to the same circuit but it makes perfect sense now with your diagram and explanation so thanks a million!

After reading your explanation I was reading another thread about the switch light feature for a light bar install. Sounds like the dimmer wire's brown in the other switches but I'll verify with multimeter prior to tapping anything.

Think the tentative plan until I test some of the empty fuse slots or run a wire to the battery or add a bus bar will be:

Red: +12v constant source tbd
Yellow: Add-a-circuit to Cig. Lighter No. 2
Red/yellow: posi-tap onto existing switch dimmer wire
Black: ground

Feeling way better about this now, will be sure to take pics/start a thread with the full install for these specific heaters and '18+ or whenever they ditched the seat heater circuit on the interior fuse panel. Thanks again @RainMan_PNW and @TNVols865

 

Never go off wire color when looking at anything but the factory EWD, and even then verify by connector and pin location.
The ILL+ is a different color depending on the switch you are looking at. And not always the same pin of every factory switch.

You have these backwards.

 

Got it, learned my lesson about trusting wire colors when hooking up a back up cam to my dad’s Silverado’s tail lights so I use either a multimeter or test light now but the ultimate wiring diagrams you posted are without a doubt the best resource.

For some reason I cannot keep those two straight in my brain lol but I’ll be sure to reference this and triple check before making any connections.

 

So I was able to determine a couple things. There's a flat 8-pin connector that's not connected to anything, unless it's supposed to be or was prior to my stereo install, but I haven't noticed anything awry in ~6 months. Within that flat 8-pin connector, pin-5 from the left is a grey illumination wire/comes on when the headlights are turned on as evidenced below:


This should good for the Yellow wire positap for switch backlight.

Using the test light on the interior fuse panel with truck off, was able to determine that two of the empty fuse slots have constant power. Attempting to read the EWD's and figure out if either of these blanks slots feed wire is good to support a 15 amp circuit. Plan on doing an add-a-circuit on Cig. Lighter No. 2 for the 5a red/yellow wire relay circuit.



On the bottom of my interior panel, I've got 4 keyed/ignition circuits:

In tracing the EWD, it looks like there's a 150A circuit that feeds a bunch of stuff (circled in green). I cut out a few of the pages in between, but if my tracing is correct, that 150A should trace to connector 3G which branches off to the 15A P/OUTLET NO. 2 circuit (circled in red) as well as 3 30A circuits for the Sliding Roof, P/SEAT, and P/SEAT F/L.



I don't see any of the 3 Sliding Roof, P/SEAT, and P/SEAT F/L 30A fuses in my panel. Assuming the sliding roof is like the rest of the windows and ignition has to be on or in the half on accessory state, which would mean with the sliding roof option that'd be one of the empty ignition circuits above, and then I'm trying to remember for power seats (I have power driver's seat but my seats are in the shop) I think power seats have constant power/you can just open the door and move them without the ignition on, which would then lead me to believe if I had power seats with factory heat etc. they'd occupy the constant fuse slots #1 and #4 above with a 30A fuse, and if so, would be perfectly safe to throw a 15A add-a-circuit into slot 1 or 4 for the +12v constant wires.

 

Was routing the wires for the heaters and while up under the dash I noticed that up on the side of the fuse panel there are 4 little square 30A fuses? Wondering if those are the 4 circled below here but in my quick googling the little tilde looking symbol indicates a fusable link so not sure if that's what they are or something different. If those 4 30A are indeed the circled functions below, guess I'll need to retrace and try and determine what the empty fuse slots are intended for.

 

I’m fairly certain those 30A are the square style you saw (and why they are noted with a different symbol) - they only use the blade style up through 25A.

 

That black connector you found behind the center trim is for the parking sonar system - so yes, that wire you found is the ILL+ circuit.
For your seat heater load, I would be comfortable grabbing any of those open spots that had constant power.

 

Was doing a little more googling and it looks like those are called "jcase" fuses, be nice if the panel cover indicated which is which although I'm assuming all those functions would be ignition circuits.

This was the short and sweet I was looking for haha, since I've got 2 empty constant slots do you think it'd be okay to tap one of them for front heaters and eventually use the other for rear heaters? Or better overall at that point (or now) to just bite the bullet and run a dedicated ~8-10 gauge wire fused at the battery to an interior fused panel like this:

 

That really depends on how much other shit you think you’re going to want to add in the future inside the cabin that needs more power…

 

I ordered one of those cause it was ~$12 and overnight delivery, found some 8 gauge in my basement and I’ve got larger fuse holders from audio projects. I should be able to get it done this weekend and I’ll decide tomorrow which route to go. Have a dash cam going in at some point as well so I might just bite the bullet and run some 8 ga for all the eventual heaters and cam but I also ordered those add a circuits you recommended cause the one I had on hand says max 10 amp. We’ll see how cold it is tomorrow and how much time I wanna spend dickin around. Add a circuit routes more appealing at the moment cause of the cold and could do that little panel come spring, either way thanks again for all the help and pointers!