2018 Seat Heater won’t turn off

[wngrog]

2018 108,000 miles.

Seat heater comes on full blast for 15 minutes then it will turn off for 10 minutes or so then it repeats.

I’ve tried pulling one 15a fuse out of the main box that kind of looked like a seat heater.

Nothing.

Pulled the inside box 30 amp for drivers seat power.

Nothing.

The switch on the console lights up normal but this is happening with all the lights off.

I’m on a road trip and this is killing me.

Something they pulls this kind of power surely has a relay but I can’t find it.

Help.

 

[clrussell]

Unplug the driver seat for now? I had to do that on my truck recently

- edit- it will likely piss off the dash unplugging the seat. But your ass won’t be on fire randomly

 

[wngrog]

The only plug I can reach without pulling seat is a yellow plug… not sure what it does.

For now I’m sitting on a My Pillow and peeling out

 

[clrussell]

The only plug I can reach without pulling seat is a yellow plug… not sure what it does.

For now I’m sitting on a My Pillow and peeling out

Yellow plug should be the airbag.

 

[bloc]

Check for water under the plastic trim at the front door sills.

Looks like its the 20A S/HTR fuse under the hood. (edit: not under the hood)

16-21 EWD

 

[Leaky2014]

I do think so.
This usually happens when you have a sunroof leak or windshield leak, pretty s***ty it happens with a cup of water, but from what I've been told on here Toyota wiring is perfect and doesn't need any protection but that's another story...

I would pull the Seat Climate Control ECU from the underside of your seat, put seat all the way forward and you can reach it.
Little black box in center of seat on underside, one connector.
I say to do this because those suckers can and will burn, ask me how I know, oh and they are around $300, if you can find one.

Then, get a fan or two in the truck to dry things out.

Then cross your fingers that the terminals don't start to corrode, they will though.

View attachment 2854407

The terminals that will corrode are in the junction box EK2, but hey, this is just my assumption, good luck.
View attachment 2854409

Disregard if the 2019 LX is different then shown.

 

[wngrog]

Check for water under the plastic trim at the front door sills.

Looks like its the 20A S/HTR fuse under the hood.

16-21 EWD

View attachment 3160796

It started after some deep water crossings.

Looks like I need to get home, pull the plastic trim and dry it out real good.

 

[wngrog]

Check for water under the plastic trim at the front door sills.

Looks like its the 20A S/HTR fuse under the hood.

16-21 EWD

View attachment 3160796

My 2018 has a 15a S/HTR and it does nothing when I pull it. Still heats up.

I pulled the kick panel off. It’s dry in there but I left it off for the rest of the Drive home just in case

 

[tbisaacs]

There is an ECU in each of the seats. If you unbolt the seat you can tip up enough to disconnect.

 

[bloc]

My 2018 has a 15a S/HTR and it does nothing when I pull it. Still heats up.

I pulled the kick panel off. It’s dry in there but I left it off for the rest of the Drive home just in case

I think the 15A fuse is for the rear heaters. Per the ewd there should be a 20 somewhere.

 

[bloc]

Also, don’t assume the water has to be on the drivers side. Check passenger side too if you haven’t already.

I’ll dig some more in the EWD to possibly get you a definitive location later today.

 

[gnob]

if the plug has water intrusion, it could be getting power from anywhere.

 

[bloc]

So these fuses should be in the right hand junction box behind the kick panel. Blue writing on the right of this image.

 

[wngrog]

Nice. Thank you sir

 

[thecapedcapper]

Were you ever able to sort this out? According to the PO of my truck (2008 LC) the driver's seat heater was stuck on so he disconnected the heater switch. Curious if it's just the switch or if there could be some other issue with the seat ecu etc.

 

[wngrog]

Nope. Mine still comes on at random times.

 

[TimCFJ40]

Were you ever able to sort this out? According to the PO of my truck (2008 LC) the driver's seat heater was stuck on so he disconnected the heater switch. Curious if it's just the switch or if there could be some other issue with the seat ecu etc.

Our 2008 had this issue where the switch stayed lighted whether the seats were on or not. I replaced the switch unit and it fixed the issue. They're pretty expensive OEM, but I bought one on Ebay from China and it worked fine.

 

[thecapedcapper]

Our 2008 had this issue where the switch stayed lighted whether the seats were on or not. I replaced the switch unit and it fixed the issue. They're pretty expensive OEM, but I bought one on Ebay from China and it worked fine.

I just bought an ebay china copy (40$ vs the 100+ for OEM and looks to be made in the same factory) so going to roll the dice hoping its the same thing.

 

[TimCFJ40]

Good Luck! It's an easy enough fix if it works!

I just bought an ebay china copy (40$ vs the 100+ for OEM and looks to be made in the same factory) so going to roll the dice hoping its the same thing.

 

[fj40alex]

My 2020 HE passenger seat heater will cycle on/off all the time. Full blast and makes for unhappy passengers. Switch doesn’t seem to matter. We have resorted to pulling the seat heater fuse - which disables both seats. It’s the fuse box in the passenger footwell area. A 20amp shown below.