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Discussion Starter · #1 · (Edited)
I’m in the middle of installing seat heaters to our Sienna.

I wanted switches that matched OEM and ended up buying a pair of Audiovox SHTOY from CarID for about $108 after tax and shipping for the pair.

So far I’ve disconnected the battery, removed the driver seat, removed the dashboard panel, and cut holes in the panel for the new switches.

Next I reconnected the battery to try and find where to get power.

I need:
  • Always on
  • Switched on
  • Lights on
  • Ground
I also removed the center console.

I’m thinking:
  • Always on - purple and white wires from under driver seat
  • Switched on - from middle row USB (red I’m guessing?)
  • Lights on - yellow from cup holder lighting
  • Ground - purple and white wires from under driver seat
QUESTIONS:
  1. After reconnecting the battery I saw a litany of dashboard failure lights. Is this normal after disconnecting the battery?
  2. Are the above wires ok to use for this?
  3. Can any of you recommend a good way to tap into the wires? I’ve been doing these sorts of things for over thirty years and I’ve never been happy with how I’ve spliced into wires.
  4. For the life of me I can’t figure out how to remove the lower plastic at the bottom of the dashboard center stack, and the first tray on the floor between the footwells. ???

Finally, I’m not happy with my results, but this is what my dash panel looks like with the switches:


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I can't help you with the wire colors but I'm curious about where the relay to power the seat heaters is located in your scheme? Your switches should act only to trigger a relay that powers the seat heaters from a robust power source. The description of the switches you bought says that one of the features is "Relay controller included".
 

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Discussion Starter · #3 ·
There is a large-ish black box that is plugged into the switches, between them and the wiring. It doesn’t look like your typical 12v Bosch automotive relay, but the relay has to be in there.

The seat heaters include 4 wires:
  • Red - always on
  • Red/Yellow - switched on
  • Black - ground
  • Yellow - illumination
One of the red wires is thicker, heavier duty, than the other wires. I think it was the always on but not sure and the wires are in the van outside right now.

I’ll grab a couple of additional pictures and add them to the thread.
 

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To what circuit are you attaching the red (always on) wire? The diagram says that it should run to the battery which means that it should be connected to a robust power source and not tied into a circuit that can't handle the seat heater electrical current draw which can be significant. For example, the two OEM seat heaters in my 2014 Sienna Limited are each on their own circuit and each of these two circuits has its own 15A fuse. Your red wire is thicker than the other wires since it is carrying the most load. Being a coward, I might run the red wire through the firewall and attach it to the accessory nut on the battery positive cable clamp which is where I power my trailer light harness and headlight washer kit. I'd put the in-line fuse in the engine compartment near the battery where it is easily accessed in case it blows ... I'd use a water resistant in-line fuse holder if I did that.

I guess you could follow the instructions and attach the Yellow illumination wire to the parking light circuit or maybe you could instead attach it to the dashboard illumination circuit so that the heat seater button backlighting will brighten and dim along with everything else on the dashboard when the dashboard lighting rheostat is adjusted. I described how I did that in post #32 in a thread about installing headlight washers: Installing Hella headlamp washers on 2014 Sienna Limited

My assumption is that the purpose for the red/yellow wire is only to tell the relay that the seat heaters can only be operated when the ignition switch is in the engine run or accessory position. Obviously your seat heater controller boxes supply the relay function even if they don't look like typical relays. Attaching the red/yellow to the USB port like you did sounds reasonable since it shouldn't draw much circuit.

It's up to you where you attach the black ground wire. You might be able to attach it to where the seat bolts to the floor to get a good solid ground.

I know they're bad but I still sometimes use old fashioned scotch lock connectors even though I have a variety of T-Tap connectors that work better when I can find where I put them. I hate to cut and solder into vehicle wires although a lot of people think that is the best/only way to properly do it.

If you want to pretty up the dashboard and your seat heater switches are exactly the same size as OEM, you could buy the bezel with precut seat heater holes as used on the XLE - part number appears to be 55446-08110 and it costs less than $30 online but verify the part number if you're interested.

I can't get a good screenshot on the laptop PC I'm using but the attached diagram for a 2019 XLE shows the lower panel and the tray I think you are talking about. I'm thinking that removing the part attached to the floor requires removing the center console but don't hold me to that.

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Discussion Starter · #6 ·
Thanks Geezer.

On my '96 Miata I added seat heaters and tapped into the power window wiring for the seat heaters power - has worked fine and not blown any fuses for 2 winters. (Did blow a fuse when I shorted the wires, but not during normal usage.)

The purple/white wires under the driver seat that I'm considering using are noticeably thicker than the seat heater wires and I suspect they'll be sufficient - was hoping someone here could chime in with a more definite answer though.

And I don't like the idea of hacking up the original Toyota wiring, but I'll probably use connectors like those in this pic just because I don't know how to do anything better and I have these on-hand. I've never heard of or seen T-Tap variants of this - I'm planning on an early morning Harbor Freight run, I'll look for those.
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My understanding of the relays is exactly the same as yours - all the relay does is detect whether or not the switch is turned on, and if it is then the relay allows the heater pads to draw power from the main, fused always-on power wire.

As for the part# for the dash panel - YES! - thank you for that. I was searching and couldn't come up with the correct part anywhere, so thank you very much for that. It's worth the $30 to me to have that piece and I'll be calling my area dealers this morning to see if any have it in stock (doubtful, but doesn't hurt to ask).

Regarding the bottom tray - I've already removed the center console while trying to locate wires to tap in to for the power. But I still can't determine how to remove the center stack plastic at the floor of the van.
 

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The purple/white wires under the driver seat that I'm considering using are noticeably thicker than the seat heater wires and I suspect they'll be sufficient - was hoping someone here could chime in with a more definite answer though.
Just be aware that Toyota's adoption of CAN bus technology is making it increasingly difficult to tap into existing 12V power sources for the purpose of powering or triggering aftermarket products. There are CAN bus circuits on my 2014 Sienna so there surely are on your 2019.

As for the part# for the dash panel - YES! - thank you for that. I was searching and couldn't come up with the correct part anywhere, so thank you very much for that. It's worth the $30 to me to have that piece and I'll be calling my area dealers this morning to see if any have it in stock (doubtful, but doesn't hurt to ask).
The retail price is $40.97. It might be less expensive to buy it online than to have a local Toyota dealer get it for you even if you have to pay shipping costs. Google the part number for places to buy it.
 

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Discussion Starter · #8 ·
Regarding the replacement dash panel pricing - absolutely correct.
Everywhere I see online shows the price between $28-$31. My local dealer just told me $53 (maybe $57, when I heard $50-something I didn't bother remembering the exact price).

ASIDE:
And they wanted $187 for the cup holder! I found the broken piece of plastic from ours when I removed the center console storage area, and the superglue is drying now as I type this. Added a reinforcement to the break using a small piece of plastic cut out from a Windex bottle in our recycling bin. Hopefully my SO will have a tougher time breaking it again. (When I told her the price to replace the cupholder she replied "Sheesh, I'll wait until the other side breaks then!")
 

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Discussion Starter · #9 ·
I’ve been working in this project since Wednesday night (it’s Saturday afternoon right now).

I’ve swapped out countless stereos in countless cars, including installing amps and CD changers in the trunks and cargo areas.

I’ve installed seat heaters in my Miata, while replacing the factory seat covers with new aftermarket leather covers

I’ve hardwired radar detectors.

I’m not new to this stuff.

But the damn Sienna is kicking my ass. I used to really like this car, and I’m growing to hate it. I respect the hell out of it - it’s a tough beast - but Toyota REALLY didn’t want people taking this thing apart.

I still don’t know how to remove the plastic tray on the floor between the footwells. Every step of the way I’ve had trouble taking the seat apart. I finally managed to remove the plastic trim around the base and am now having trouble removing the actual seat covers in the bottom of the seat - how do I get to the clips securing the sides?

Working on the interior of this car is a miserable experience and I’m wishing I’d just paid a shop and accepted whatever half-assed job they turned in.
 

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I still don’t know how to remove the plastic tray on the floor between the footwells.
Have you removed the side panels in the footwells forward of the floor tray assembly? Based on the diagram I posted for you, it looks like the tray assembly and these two side panels are joined - maybe with tabs that slide into slots.

I don't see any other fasteners in the diagram that might be holding the floor tray assembly in place other than the four removable clips on the sides in the footwells and the two bolts visible after you removed the console. It might be a necessary to use an uncomfortable amount of muscle to jerk the floor tray assembly out. Heck, half the interior is held in place by clips and tabs that slide into holes and slots which is also largely how the front and rear bumper covers are held in place.
 

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I still don’t know how to remove the plastic tray on the floor between the footwells. Every step of the way I’ve had trouble taking the seat apart. I finally managed to remove the plastic trim around the base and am now having trouble removing the actual seat covers in the bottom of the seat - how do I get to the clips securing the sides?
The Toyota interior is like a puzzle. Once you know how the pieces go together, then disassembly becomes very easy.
If you are referring to the plastic tray on the floor between the driver and passenger seats, then on the 2013 XLE, you need to remove the middle console first which is held by 4 bolts. Once that is out, the plastic tray can be removed by pulling towards the rear after removing a couple of plastic fasteners.
All in all, it takes less than 15 minutes to remove the entire middle and lower front console.
 

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Discussion Starter · #12 ·
Thanks guys. Yeah, the center console is removed, and the two plastic ‘screws’ in the sides of the vertical side panels are removed.
I’m probably just not tugging with enough force - was scared of breaking the clips. I’ll give it another try once I’m done recovering the seat and am on to the wiring part of the program.

Thanks again.
 
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