Swapping OEM heated seats for Scheel Mann heated seats

There is another thread about getting Scheel Mann seats into your 2nd or 3rd gen Taco here:
https://www.tacomaworld.com/threads/tacoma-occupant-sensor-bypass.739762/

I want to go one step further and integrate the factory heated seat controls into the heated Scheel Mann seat.

Some new codes that showed up, indicating I have heated seat circuit malfunctions. I do, those parts from the stock heated seats are not ported over to the Scheel Mann seats. So that plug in the vehicle harness has nothing from the seat connected to it anymore. But this is after nearly 18 months without these codes???

B14C0
Front Right Seat Heat Sensor Circuit

B14C1
Front Left Seat Heat Sensor Circuit


The Scheel Mann seats are heated and have a separate micro-controller. But I want the stock heated seat dash buttons with 3 heat settings, to work with my Scheel Mann seats, with only 2 heat settings.

My best idea so far is to A) first ensure the wires that do the resistive heating are compatible between the two seats. Things like the wire gauge and expected voltage/current etc. Then, B) simply cut the heated seat wires from the stock brain output, and attach them to the Scheel Mann seat wires. The sets of wires are exposed near the back of the seat, on both seats, where the elements enter the foam of the seat top and bottom. So this would bypass the Scheel Mann controls/controller and use everything stock except the seat wires themselves in the Scheel Mann. Then I would retain the factory dash button functions with 3 heat settings, and the seat harness connection.

I am sure I can get more specs from Scheel Mann. I also know someone near me that has a pair of the Scheel Mann heated seats setup and working. So I could test a standard Scheel Mann setup, and a standard Tacoma heated seat setup.

@caribe makaira any thoughts on this? Appreciate the help!

The stock Tacoma heated seat brain has two sets of wires, one going to the seat bottom and one going to the seat back. The one going to the seat back is just 2 wires, but the one going to the seat bottom has 3 wires (red, black, white). So that is my current confusion, what is the 3rd white wire for in the lower portion of the seat? Figure L above shows the two 2-wire connectors that I could wire into the stock seat wires. Except that 3rd wire on the lower... gotta figure out where that goes.

 

Picture of the passenger side heating plug, amp, and wires/circuit.

 

This is what I think I would do. But its not clear to me what the 3rd wire coming out of the bottom seat cushion heating wire set is for? Best I can tell its a ground? I'm trying to decipher the schematic from @caribe makaira but my wire colors are not the same?



This schematic also shows a single AC Amp used by both seats, where my seats each have their own. You can see the small Gentherm Amp in the pic - one under each seat.

I see that the Scheel Mann relay is rated to 40a. But that is per seat. So if the 20a rating from the Toyota schematic is accurate, and its for both seats, then I think the Scheel Mann seat could take more amperage than the Toyota seat. But since I'd be using the Tacoma side to power everything for this solution, we'd only care that the wires in the Scheel Mann are beefy enough to take what the Tacoma will send it, as far as power/gauge/volts/amps. And that should be the case, then. Perhaps the Scheel Mann's powered by the Tacoma circuitry will not heat up as much?

 

My opinion, stay away from tying into the OEM heater circuit of the vehicle. Install the seat heater as per instructions of the manufacture.

 

Noted. Is this the correct schematic for a 2020 Off Road w/ Heated Seats?

 

Wire color change might be an issue, but system, connectors, etc. are same from other years. (3rd Gen)

 

The schematic seems to show a single AC Amp used for both seats, but I think I have 2 separate amps, one for each seat. I can follow pin number to match the wire colors or use a multimeter to know more. But the wiring around the Amp is confusing?

 

Like I posted, don't mess with the vehicle circuit. The A/C panel might get hosed.$$$
What you are calling amp is in fact a relay

 

The A/C Amp in the heated seat schematic is for the air conditioning?

 

Where in the schematic are the wires leading into the seat cushions represented?

 

What I refer to as an Amp is labeled with the word "Amp" in both cases. Maybe it is really a relay instead? From what I can tell the Gentherm 585W Seat amp is simply not shown in the schematic provided. I wouldn't know why the Air Conditioning amp is integrated with the seat heating circuit, but it doesn't matter. I am not truly messing with the heated seat circuit, I am simply swapping the last mile of wire that does the heating. All the stock circuitry, brains, relays, switches, voltages, amperages, etc remains identical. Thats part of the point of my inquiry, to remove codes being thrown by the stock circuit not being present/complete due to the seat swap. I am trying to restore that circuit so the codes go away. And of course, also have my cake too by having the heated seats actually work.

What is the 3rd wire coming into the bottom seat cushion?

I am content to sacrifice my stock seats in the name of science. I will be removing the wires and tearing apart the lower seat cushion to find out. It would just be nice to have more information before continuing.

 

The A/C amplifier has something to do with the heat control...

 

Sorry if this is a dumb question...
Is there legend data missing that may be earlier in the documentation?

What do the B, B, TH, E, E values stand for?

B1, B, TH, E, E on the RH cushion, etc

 

E = Ground
B = Power
TH= Thermistor

I'm out.

 

Ok but at the very least, I need to plug the vehicle side back into this harness so the codes are no longer thrown. The 2 wires going to the upper cushion are on a plug, so I can disconnect those. But the 3 wires going to the lower cushion do not have a plug, so I'd have to do *something* with those. Even if I have to install the standard Scheel Mann heating system otherwise. Also, I don't know if there needs to be resistance there off the 2 wire plug or any of the 3 wires that go to the lower cushion.

 

Makes sense if the dash buttons for the seats are a part of the AC control unit - thanks for bearing with me!

 

It looks like the 3 wires for the bottom are used by a pad that is stapled to each corner between the seat pleather and the cushion. It looks like the pad is self contained and would come out, so in theory I could just remove that entire pad and have an upholsterer place it in the same position in the Scheel Mann.