Second row heated seats - Toyota Sienna Forum - siennachat.com
 
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post #1 of 9 (permalink) Old 12-22-2016, 11:31 PM Thread Starter
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Second row heated seats

After getting into our Sienna Sunday morning when it was -14 degrees F. and the wind chill was -31 degrees F., even my wife thinks it would be nice to have seat heaters in the second row.

Installing carbon fiber seat heater pads in the seat cushions and backs and installing the switches on the inboard front corners of the seat cushion trim panels seems easy enough - except for removing/reinstalling those incredibly heavy "lounge seat captain's chairs with long-slide feature". I removed them once by myself and will never do that again without help.

The main challenge is how to route the power and ground wires for the heaters to the seats while preserving the "long-slide feature" without the wires showing and being subject to damage as the seat is slid from its front most to rear most position.

I have studied interior photos and parts diagrams for the Toyota Alphard Executive Lounge which has a long-slide feature for its second row captain's chairs (they are more like thrones!) which have power-everything ... recline, massage, footrest, table. The wire bundle for the second row Alphard seats appear to be inside the seat track channels in the floor. I suspect that the wire bundle for the Alphard 2nd row seats might be fairly large due to the many electrical functions and I'm guessing that the channels in the Alphard floor are deeper than the Sienna's to make room for it.

It doesn't look like I can hide the wires for the 2nd row seat heaters in the seat track channels of the Sienna due to their not being enough room and the possibility (or probability) that moving the seat would damage the wires.

What I'm thinking about doing is to run the wires for each second row seat heater from the front of the vehicle under the carpet and have them exit up through the carpet just aft of where the bottom edge of the retracted foot rest is when the 2nd row seat is slid as far rearward as it goes. I think having the wires exit at this position would allow the seat to be slid all the way forward with the seat heater wire exit point from the carpet then being just below the rear of the seat cushion. The arrow in the attached photo is pointed to just ahead of where I would slit the carpet for the seat heater wire to exit from below the carpet.

Any suggestions on how to route the wires or anything else on this project?

If I don't talk myself out of the project, I will use Dorman carbon fiber seat heaters since they seem to get the best reviews for reliability and function although they are pricier than most. Maybe I'm lucky that Amazon is out currently out of the Dorman kits although more will be arriving soon. Demand for them might have increased due to the recent weather.

If this project goes well, I might try to put seat heaters in the third row - outboard seats only. Routing wires into the third row seats should be easier since there are already wires for the power recline feature and I assume I can run seat heater wires alongside those. I would put the seat heater switches on the front outboard corners near the recline switches.
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File Type: jpg Tentative location of seat heater wires.jpg (64.2 KB, 65 views)

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post #2 of 9 (permalink) Old 12-23-2016, 07:34 AM
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Re: Second row heated seats

Sounds like a great mod on a car with leather.

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post #3 of 9 (permalink) Old 12-28-2016, 12:47 PM
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Re: Second row heated seats

I'll be interested in seeing what you come up with. We're still waiting on our SE but I have a pair of heated seat kits in the garage and the idea of putting them in the second row had crossed my mind.

I think you've got the right idea with the wire routing. If the seats just cover the wiring exit in the rearmost position and you leave enough slack for them to go all the way forward the wires shouldn't be too visible. You could also attach your wiring loom to the bottom of the seat with some stretchy 'shock cord' to keep a bit of tension on it so it stays under the seat base in all positions. Having a quick disconnect in the wires might be a good idea too in case you do need to remove the seats again in the future.
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post #4 of 9 (permalink) Old 12-28-2016, 03:13 PM Thread Starter
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Second row heated seats

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Originally Posted by 96r50 View Post
I'll be interested in seeing what you come up with. We're still waiting on our SE but I have a pair of heated seat kits in the garage and the idea of putting them in the second row had crossed my mind.

I think you've got the right idea with the wire routing. If the seats just cover the wiring exit in the rearmost position and you leave enough slack for them to go all the way forward the wires shouldn't be too visible. You could also attach your wiring loom to the bottom of the seat with some stretchy 'shock cord' to keep a bit of tension on it so it stays under the seat base in all positions. Having a quick disconnect in the wires might be a good idea too in case you do need to remove the seats again in the future.

Since you already have two seat heater kits, I think you should go first so I can learn from your experience!

So far, I've mainly just peered under the 2nd row seats to try to determine how the seat cushions are attached and to verify that there is clearance for installing the switches on the inboard front seat trim corners. I'd like to get this project done by no later than mid-February so that we would get some use from them this winter.


I may have a local auto accessory/audio shop install the seat heater pads and then I would install the switches and do all the wiring - the same company that tinted the windows of numerous vehicles for us and which once did the final connections for a vehicle phone system when I was a bit laid up. Those 2nd row ottoman seats are incredibly heavy - I strained my back the one time I removed them.


I've thought about using "shock cords" or even some sort of "reel" to take up wire slack although I'm confident that the wires won't show unless the leg rest is up. I still have a few nearly indestructible olive drab color elastic bands for army fatigues from almost 50 years ago that might work - I'm a major packrat.


Especially robust (i.e. hard to break) connectors are needed for connecting the seat heater pad/switch harness to the wires running under the carpet so that the 2nd row seats can still be removed. Unless I come up with something better, my plan is to use "flat-four" trailer light harness connectors as they are sort of rubbery, nearly impossible to break, and attach together firmly. If necessary, I can use small cable ties to ensure that the male and female connectors do not separate as the seat is slid forward and backward. Flat-four connectors with their attached wire pigtails are inexpensive and available at trailer supply stores, online and I think even at Walmart.


Thank you for your reply - it gets me back to thinking and planning which is where the fun is.

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post #5 of 9 (permalink) Old 01-05-2017, 11:34 PM
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Re: Second row heated seats

Quote:
Originally Posted by Geezer1 View Post
Since you already have two seat heater kits, I think you should go first so I can learn from your experience!

Especially robust (i.e. hard to break) connectors are needed for connecting the seat heater pad/switch harness to the wires running under the carpet so that the 2nd row seats can still be removed. Unless I come up with something better, my plan is to use "flat-four" trailer light harness connectors as they are sort of rubbery, nearly impossible to break, and attach together firmly. If necessary, I can use small cable ties to ensure that the male and female connectors do not separate as the seat is slid forward and backward. Flat-four connectors with their attached wire pigtails are inexpensive and available at trailer supply stores, online and I think even at Walmart.

Thank you for your reply - it gets me back to thinking and planning which is where the fun is.
I would, but I don't even have the van yet. Once it gets here those two seats will have child seats in them for at least another 5-6 years so I'm really in no rush

You can also get flat-two connectors which would be perfect for this as you're only supplying power and ground to the heaters since the switch will be onboard the seat as well. The flat-two's should be easier to hide under the floor or trim panels too.

Agreed, I find the planning and hypothesizing is at least as much fun as actually doing the project! Please keep us in the loop as your project progresses.
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post #6 of 9 (permalink) Old 01-06-2017, 11:56 AM Thread Starter
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Originally Posted by 96r50 View Post
You can also get flat-two connectors which would be perfect for this as you're only supplying power and ground to the heaters since the switch will be onboard the seat as well. The flat-two's should be easier to hide under the floor or trim panels too.

Excellent suggestion - I hadn't thought about using those but something has come up that might mean that four or even five wires to each seat will be required - two wires to the seat heater and two or three wires to a remotely mounted seat heater switch.


I've spent countless hours reading forum threads on installing seat heaters in front seats and watching "how-to" videos on YouTube but I haven't found anything on doing it in 2nd row seats. A challenge in many vehicles including the Sienna are the upholstery "listings" - the upholstery seams that attach to metal rods with hog rings to hold the upholstery tightly in place.


Some who have installed seat heaters in seats with "front to back" listings like in the Sienna have not reattached the center listing in order to avoid cutting a slot for the listing in the carbon fiber seat heater panel. That method may be "good enough" for some but it's not for me - looks too sloppy. The Dorman seat heaters I had planned to use are square, aren't that large and might require cutting slots for all three listings. I now think that a "longer and narrower" carbon fiber seat heater panel would work better since it would just fit between the two outer listings and require cutting one slot for the center listing. A long/narrow carbon fiber panel would also leave enough of the electrical circuit intact at the front and back of the seat cushion and the bottom and top of seat back for adequate electrical conductivity after the one slot is cut.


I took my Sienna to a professional installer a week ago today. Oh ... my! He's even older than I am and we mainly talked about why we still wanted to work past the age where most have retired.


The installer had experience installing seat heaters in the second row seats of SUV's but had never installed them in ottoman seats like the ones in the second row of the Sienna Limited that slide forward and backward so much. He pointed out that the plastic trim panels on the sides of the ottoman seats are different than the ones on the front seats. The front seat cushion plastic trim panels are essentially formed slabs of one layer plastic at the front corners while the front corners of the plastic seat cushion trim panels on the 2nd row ottoman seats have two layers with a void between the two layers. There is plenty of clearance for seat heater switches in the corners of the front seat cushion trim panels but maybe not in the 2nd row ottoman seats.


I wanted to have the round seat heater switches on the inboard front corners of the ottoman seats but the void between the two plastic layers may not be deep enough for the switch and the connector from the kit's wiring harness. There is significantly more space between the two plastic layers on the outboard corners of the seats but mounting the heater switches there might interfere with the leg rest release lever. The main reason I wanted the seat heater switches on the inboard corners of the ottoman seats is so I could see from the driver seat if someone had inadvertently left them on and be able to reach back and turn them off.

The installer told me that he would rather put the seat heater switches at the back of the center console ... until I showed him that the rear of the center console slides forward and backward. He was concerned that he might not be able to hide the wires for the seat heater switches in the sliding console until I mentioned that there must already be wires to the back of the sliding console for the audio/video inputs and the 110V outlet. He also said that he has carbon fiber seat heater pads that come pre-cut for the center listing. Someone else at the business told me that they use seat heaters from "Roadwire".


So ... the installer said that he would do the job for $700 if he could put the seat heater switches at the back of the center console. I had originally wanted to do the wiring myself but I can see why he wants to do the entire job to ensure that everything functions properly.


I really, really don't want the 2nd row seat heater switches in the back of the center console including for the reason that they would be impossible for 2nd row passengers to reach when the console is in the forward position and the ottoman seats are in their rear most position. My next step is to use my borescope to see how much clearance there really is in the voids in the ottoman seat cushion trim panels. I need to know the exact dimensions of the switches and their connectors which I assume I can get by asking on Amazon.com. If I could wave my magic wand, I'd put the seat heater switches just aft of the power window switches in the sliding door but that's not realistic.


The outside thermometer in the Sienna read zero degrees Fahrenheit this morning on the way to work. It was warmer in my garage but still too cold to mess with this project.

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Last edited by Geezer1; 01-06-2017 at 11:58 AM.
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post #7 of 9 (permalink) Old 01-10-2017, 05:25 PM
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Re: Second row heated seats

Have you been able to verify that the second row seats have these listings running front to back? If I recall correctly when I did heated seats in my Land Cruiser the leather seat covers had the listings down either side of the centre seat cushion but nothing running across the middle of the seat. There was stitching running across them but it was only for show and not used as attachment points. That centre front-to-back seam may be the same.

If it is a listing you can always cut a small hole or "X" in the seat heater element every so often and attach a hog ring or zip tie through the hole. You only lose a few heating wires this way and still retain the integrity of the seat. Your passengers butts will never notice!

Is there any downside to drilling out the second layer of plastic to fit the switches in the location you would prefer? I think that is likely the best location for the switches for all the reasons you mention. If you disconnected your seats from the van and just laid them down backwards could you see the two layers that way?

Not having my van yet is killing me because I can't go out and poke around the second row seats and see what you're talking about. I suppose my SE seats will be different than yours but it would help scratch the itch nonetheless!
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post #8 of 9 (permalink) Old 01-10-2017, 11:26 PM Thread Starter
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Re: Second row heated seats

Quote:
Originally Posted by 96r50 View Post
Have you been able to verify that the second row seats have these listings running front to back? If I recall correctly when I did heated seats in my Land Cruiser the leather seat covers had the listings down either side of the centre seat cushion but nothing running across the middle of the seat. There was stitching running across them but it was only for show and not used as attachment points. That centre front-to-back seam may be the same.

If it is a listing you can always cut a small hole or "X" in the seat heater element every so often and attach a hog ring or zip tie through the hole. You only lose a few heating wires this way and still retain the integrity of the seat. Your passengers butts will never notice!

Is there any downside to drilling out the second layer of plastic to fit the switches in the location you would prefer? I think that is likely the best location for the switches for all the reasons you mention. If you disconnected your seats from the van and just laid them down backwards could you see the two layers that way?

Not having my van yet is killing me because I can't go out and poke around the second row seats and see what you're talking about. I suppose my SE seats will be different than yours but it would help scratch the itch nonetheless!
Yes, I could probably drill through both layers of the plastic on the ottoman seat cushion trim. I might have to position the switches further back than I want to ensure that they don't interfere with the retraction of the leg rest and the seat adjustment mechanisms.

I haven't disassembled the seat cushion upholstery but it looks like there is a center front-to-back listing attached with hog rings that holds the leather upholstery tightly to underlying seat structure. I think I can tell where the center listing rod "ends" near the front and back of the seat cushion and the bottom and top of the seat back. You can see the center listings in the photo I posted earlier in this thread.

There seems to be significant differences in how Toyota seats are designed, where the listings are on them and the number of listings they have. Many Toyota seats have listings that run across the seat cushion and back rest. I got a bit hyped when I found a Rostra seat heater kit specifically designed for a recent Toyota Camry series until I found that the Camry seat listings are completely different and run across the seat cushion and backrest.

Based on the photos in 2015-up Sienna brochures, I wonder if the seat listings in your 2017 Sienna SE will run across the seats like in the Camry.

I learned since my last point that a carbon fiber seat heater element should not be slit front to back to allow for attaching hog rings. As you noted, a small hole (Rostra install instructions call them "windows") should be cut in the carbon fiber heater panel where each hog ring has to be reattached.

I'm starting to reevaluate the priority of this project since a driver of this project is for my wife who sometimes likes to recline in a 2nd row seat on long trips. I don't know how she stands it but she always has to have her seat heater going full blast. She has a bunch of plug-in heating pads she uses for therapeutic purposes and I now wonder if the 120V outlets in the Sienna would power them - sure would be easier than installing seat heaters although it would be nice to have them for others. Of course I could just get an external 12V heated car seat cushion for her - they're cheap and even Bed, Bath and Beyond sells them.

As sloppy as the weather has been lately, headlight washers would be a lot more useful - at least I have experience installing them. Here is a photo of a Sienna in Switzerland with a Hella 8WS 008 549-001 headlight washer kit - the owner installed only two of the four spray nozzles that come with the kit. The Hella headlight washer kit links to the windshield washer.
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File Type: jpg Gen 3 Sienna with Hella 8WS 008 549-001 headlamp washers.jpg (40.8 KB, 15 views)

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post #9 of 9 (permalink) Old 01-11-2017, 02:42 PM
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Re: Second row heated seats

Quite a few heated massaging seating pads is only $20 or so, if anything I rather do a bigger power inverter for the van. The headlight washer is a great idea but with the Sienna headlights kind of big, you really need 4 of them to be effective. even better if the nozzles are paintable to body color or retractable like the Lexus RX ones I have.
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