Wiring Gurus, please help!

Couple of questions here. Please help wherever you can.

2019 SR5 2WD. Recently installed Clazzio leather seat covers with heat elements and the “Toyota style” switches. Plan on using add a fuse to get them in my truck, but have held off on wiring to ask a few questions (pictures of harness for heaters and my fuse box below):

1) I have no need to run the heaters with the truck not running. Can I combine the “On” wire with the main power and tap into a fuse that only runs when the truck is in the “On” position, and only have the seats work when the truck is running?

2) Tying into that, would it be ok to also throw the illumination wire into that same add a fuse? I’m trying to avoid adding 4-6 fuse taps.

3) My truck was purchased used, and I have realized that my fuse box cover (with the diagram) is MIA. Also, there is already a fuse tap there which is connected to nothing? (Guessing previous owner took something out and left the tap). Can someone tell me if the fuse box is the same in all trim levels? Don’t want to go off a stock photo from somewhere and accidentally tap into ABS or Airbag systems.

4) Being an SR5 2WD, there are a lot of open slots. Is it ok to use those (I.e. are they going to be functional)? For instance, if there is a seat heater spot, and I didn’t have factory heaters, would that be the best spot to use? Just looking for advice on where to tap in and have it work without hurting the truck.

Sorry for the blast of questions, but I’m just not accustomed to tapping into the fuse box (obviously). Thanks for any help you can provide!

 

I’m trying to figure out how the seats are heated?
Through a relay?

Either way, each seat draws 5A
And 2 seats would draw 10A

I’m not sure I’d want to add that much to any existing circuit.
When in doubt, I always choose to go with a relay.

 

This is a job for: @caribe makaira

 

2 Separate relays for each seat. Forgot to mention that. So this picture is one harness for one seat.

 

This: i don't think there's an issue using an add-a-fuse to an existong circuit to feed the switches and then using the switches to control a relay, but for that power draw you do really need to add an additional circuit to handle the power delivery.

 

How are you planning to run the main power wire (big wire)
From the battery or from an existing empty spot in the fuse box?
If you are looking to tap from the fuse box, I can’t help there.

But if you go from the battery, then I might be able to find a fuse that is Ignition On only for the trigger wire. (Switch)

 

Clazzio is VERY fuzzy on installation instructions themselves, but customer service (and several install videos) recommended the add-a-fuse tap. Saw one that used both red wires into the add a fuse, which is why I added that part of the question.

 

Yeah, definitely good that you asked.
I wouldn’t use an existing circuit to power the heaters.
That’s a lot of extra current and will probably over load the circuit.
Best case blow a fuse, worst case melt stuff.

I’d run the main power wire for the heaters from the battery.
Unless @caribe makaira knows of a better place to tap.
That guy knows his way around Toyota wiring. He might know a better idea.

 

If going off the battery- put a fuse on the battery end also- 15a if running both 5a seats on it. Be sure you are running the proper gauge wires for the total length of wire you run to the seats-
See this calculator:
https://www.wirebarn.com/Wire-Calculator-_ep_41.html

Also be very careful if running it through the firewall in an existing grommet hole that also has a harness or other wiring in it.

 

NOoooo!
…well, unless you really know what you are tapping into and the load the wires running into it are designed for.

 

That’s why I’m asking all these questions. I was honestly eyeballing the S/HTR and S/ROOF 20A fuses on the lower left of this diagram, since I don’t have either of those accessories. Seems like ample power, but I just wanted reassurance that I wasn’t going to burn the truck down.

Sounds like a larger gauge wire directly to the battery and feeding both of the main power supplies is best, from what you are all recommending? And for the “On” wire (small red) and the switch illumination (little yellow) should I use the taps for those?

 

You could use a tap for the control wire through the switches to turn on/off the relay. I didn’t notice that 20a s/roof circuit- are you sure it’s being used and is active? I’d still put a 5a fuse on next to the tap near the box when using that to control the relay, and a 15a next to the battery for the power lead.

 

I added the same heaters. I grabbed a plug off of Amazon for the brake controller and used that circuit to power the seats. It's 40 amps and already fused. It also provided the illumination circuit. Forget what fuse I used (you can see it in the second pic) but used a tap just to trigger the system on/off with the truck.

The power from the brake circuit was run into a small fuse panel and individual fuses were used for each seat and the lights. Was easy and didn't require running power from the battery. This is assuming you won't be adding a brake controller in the future.

 

Gonna have to throw the multimeter on the box to see what is active. Seems like they wouldn’t put a fuse there for seat heaters for nothing, but that is kinda why I was on here looking for someone who did this before me.

 

@UNCATC was you able to get yours installed. I am wanting to do the same and after all my searching I think I can wire them up like this. Ground of course going to a ground bolt in cab somewhere. The smaller red wire labeled on switch going to tap my cigarette lighter plug. The main battery wire straight to battery with a fuse just in case. And lastly the yellow wire going to this ECT/Auto high beam jumper wire I found on here people mostly use to illuminate a switch for light bars