LEXUS GX SEAT SWAP INTO FJ80 PROGRESS / WIRING HELP

[WMaher]

LOOKING FOR HELP WITH HEATED SEAT WIRING

Some background, trying to install GX 470 seats into my 1993 Toyota LandCruiser, I have every single function of the seats to work besides the heated seats(slide/lumbar/tilt/ect).
I have the wiring diagrams for the GX and I will be running separate circuits so the LandCruiser wiring shouldn't be in the question. Reaching out to yall on here in hopes of finding help as Im wasting too much time trying to figure out something that seems very simple. I also have OEM lexus GX heated seat scroll switches with their pig tail harness, and still haven't had luck.

*see picture of wiring diagram*
My question is, shouldn't all I need to do to get the heated seats to turn on is provide power (+ to black / - to white) that goes into the seat heater, and then bridge brown and red wires that come out of the seat heater? I have provided power to the rest of the seat (including seat ECU SW) while trying this with nothing, I have also tried the OEM heated seat switches wired as the diagram shows with no luck as well.

If anyone has any advice it'd be greatly appreciated as Im about to give up on the heated seat function. I have attached screenshots of both the heated seat wiring and the power seat (drivers) wiring.

If anyone is curious about doing this seat swap, I would advise against it and urge to find a bolt-in solution, total cost will be right around 600$ (350$ for seats in good condition + 120$ OEM heated seat switches + metal/materials) and was a ton of fabrication work for me, although I'm doing this out of my garage and someone with a press break and a CNC plasma cutter could do it in a fraction of the time.

 

[NeverFinis]

Just so you know, the last image is the most important one and it is cropped. I fully can't tell what is coming into/out of the heated seat circuit.

The heater switch appears to have a variable resistor to regulate heat. I would measure terminals 2 and 3 to see see what the resistance (Ohms) is on min and max settings.

The heated seats might not be designed to take the full +12V from the battery. Also, have you confirmed you have the heater element?

Is there a resistance across the B and W-B wires when BR and R wires are connected?

 

[Malleus]

You're missing the ground. The switches you're using are grounded through the harness, which you don't have (this is why you seat functions work - the ground they're using is in the harness). Run a separate ground to the ground point under the console for the heater switch.

 

[WMaher]

Just so you know, the last image is the most important one and it is cropped. I fully can't tell what is coming into/out of the heated seat circuit.

The heater switch appears to have a variable resistor to regulate heat. I would measure terminals 2 and 3 to see see what the resistance (Ohms) is on min and max settings.

The heated seats might not be designed to take the full +12V from the battery. Also, have you confirmed you have the heater element?

Is there a resistance across the B and W-B wires when BR and R wires are connected?

Sorry for cropping it, I attached the PDF of the seat heater, I haven’t measured resistance or ohms of the switch but I will tonight. From my understanding yes I have the element, every GX came with heated seats and I have verified wires that run into the actual seat cushion themselves that would align with it having a heater

 

[WMaher]

You're missing the ground. The switches you're using are grounded through the harness, which you don't have (this is why you seat functions work - the ground they're using is in the harness). Run a separate ground to the ground point under the console for the heater switch.

So you’re saying I need to run the ground from my switches to a common ground on the wiring harness of the seat? Instead of just a body ground?

 

[Malleus]

No, use the body ground under the console. It's in the EWD.

 

[NeverFinis]

Sorry for cropping it, I attached the PDF of the seat heater, I haven’t measured resistance or ohms of the switch but I will tonight. From my understanding yes I have the element, every GX came with heated seats and I have verified wires that run into the actual seat cushion themselves that would align with it having a heater

Thanks.

You also want to verify the resistance of the heating element as well. It might be shorted out (0 Ohms), or not even there. Toyota did install harnesses even if the option was not installed.

I just don't know what the variable resistor in the switch is designed to do. It regulates power to the heating element, which means it is down regulating voltage. The max heat setting might still have resistance from the switch, which means it could even be dropping the voltage at max heat, and drops it further with min heat. I think this is unlikely though.

Battery Pos and Battery Neg should have been fine for testing B (Pos) and W-B (Neg) as long as BR and R were tied together, notwithstanding what the switch is doing.

 

[WMaher]

Thanks.

You also want to verify the resistance of the heating element as well. It might be shorted out (0 Ohms), or not even there. Toyota did install harnesses even if the option was not installed.

I just don't know what the variable resistor in the switch is designed to do. It regulates power to the heating element, which means it is down regulating voltage. The max heat setting might still have resistance from the switch, which means it could even be dropping the voltage at max heat, and drops it further with min heat. I think this is unlikely though.

Battery Pos and Battery Neg should have been fine for testing B (Pos) and W-B (Neg) as long as BR and R were tied together, notwithstanding what the switch is doing.

Havnt done any more testing with switching grounds or anything yet, but I did measure resistance from several points, Ill attach some of the pics below.
Drivers Seat:
Black and White wire with nothing crossed- 7.12 ohms
Black and White wire with Red and Brown crossed- 0 ohms
White and Brown with none crossed- 8.27 M ohms
White and Red with none crossed- 8.29 M ohms
Black and Brown with none crossed- 28.54 M ohms
Black and Red with none crossed- 29.7 M ohms
Passenger Seat:
Black and White wire with nothing crossed- 5.59 M ohms
Black and White wire with Red and Brown crossed- 0 ohms
White and Brown with none crossed- 8ish M ohms
White and Red with none crossed- 8ish M ohms
Black and Brown with none crossed- 39.83 M ohms
Black and Red with none crossed- 23.18 M ohms
Switch
Red and RedGreen at full heat- 337 ohms
Red and RedGreen at off- 3.418 K ohms

If you can make any sense of this that'd be awesome, I haven't tested the passenger seat yet but from what I'm getting for resistance, unless both heated elements are fried then I think they are both there and "could" work. Although I am confused as to why I get resistance with the Brown and Red open, and no resistance with them closed.

Thanks again

 

[clx16]

I am not sure where your cut is at in this harness but connector J36 which connects to j37 (just talking about the one seat) is represented 2 times in that wiring diagram as that connector represents the circuit connecting the heating element... the wiring diagram shows it logically in the middle of the circuit but physically the element is in the seat and the rest of the circuit is on the other side of the actual plug. This means the power comes in via the LG (light green) and is grounded by the WB (white with black)at the end. But first start with the flow and follow LG (light green)up to the j36>j37 via the B (black) wire through one side of the element and out via (B) Brown,, back through that plug but the other direction j37>j36 and out R (Red) to your variable switch (REMEMBER that switch is powered by an Ignition Relay---probably really ACC--- to enable the circuilt when the key is turned). That switch connects the R (Red) to RG(Red with Green) down to the connector again J37>J36 where it turns R (Red) again Through the element other side where it goes to ground WB (white with black) and continues through the connector again until it gets to that body ground. That element is part of the circuit with the switch in the middle of it. both sides of the element are connected via the variable switch.

that switch has an LED in it and likely will never show as completely open as far as resistance goes. That entire circuit shouldn't get power until that relay is activated from the Blue IG source (10A) you see in the diagram. that 10A IG source just enables the 20A circuit to power the heaters. (This tells you what size fuze you should use here)

Do not use the same power on the IG side of the diagram as you get for the moving the seats as those are on all the time regardless of if your vehicle key is turned on or off (in most situations you can adjust the seats in a vehicle before you get in and even put in a key). You do not want your heated seats to be able to be turned on when the vehicle isn't running as people often forget to turn those off when they exit a vehicile.

I hope this helps.

in short the switch is between the Red and Brown and the black is your power in. as mentioned you can connect the red and brown and move the switch to either black or the white black (ground) wire but you will still want a relay that is triggered by the ACC at least to enable the ciruilt.

 

[NeverFinis]

Havnt done any more testing with switching grounds or anything yet, but I did measure resistance from several points, Ill attach some of the pics below.
Drivers Seat:
Black and White wire with nothing crossed- 7.12 ohms
Black and White wire with Red and Brown crossed- 0 ohms
White and Brown with none crossed- 8.27 M ohms
White and Red with none crossed- 8.29 M ohms
Black and Brown with none crossed- 28.54 M ohms
Black and Red with none crossed- 29.7 M ohms
Passenger Seat:
Black and White wire with nothing crossed- 5.59 M ohms
Black and White wire with Red and Brown crossed- 0 ohms
White and Brown with none crossed- 8ish M ohms
White and Red with none crossed- 8ish M ohms
Black and Brown with none crossed- 39.83 M ohms
Black and Red with none crossed- 23.18 M ohms
Switch
Red and RedGreen at full heat- 337 ohms
Red and RedGreen at off- 3.418 K ohms

I put the ones I think are important in Bold and used a bigger font.

The megaohms readings are probably open circuits and could probably be ignored.

The Driver's B <-> W reading 7.12 ohms equates to 20 Watts of power. Is this right? However, I would have expected this with Red and Brown connected...

The fact that the driver and passenger B <-> W readings are different might indicate an issue, or just a misreading.

The switch at full heat reading 337 ohms seems is interesting. Knowing that now and for testing without the switch in place, I would personally use a 330 ohm resistor between Red and Brown and then apply power across B and W-B.

The seat heater might have circuitry in it that reads the voltage coming from the switch. To me, this would be smart as it would mean power wouldn't have to flow through the switch....just enough to change LED brightness.

Speaking of that, the switch's LED does uses the variable resistor for brightness and that is all I think the switch needs for power.

Hope that helps.

I am sure the manual has a Diagnostic section for the heated seats...might be worth a look.

 

[WMaher]

I am not sure where your cut is at in this harness but connector J36 which connects to j37 (just talking about the one seat) is represented 2 times in that wiring diagram as that connector represents the circuit connecting the heating element... the wiring diagram shows it logically in the middle of the circuit but physically the element is in the seat and the rest of the circuit is on the other side of the actual plug. This means the power comes in via the LG (light green) and is grounded by the WB (white with black)at the end. But first start with the flow and follow LG (light green)up to the j36>j37 via the B (black) wire through one side of the element and out via (B) Brown,, back through that plug but the other direction j37>j36 and out R (Red) to your variable switch (REMEMBER that switch is powered by an Ignition Relay---probably really ACC--- to enable the circuilt when the key is turned). That switch connects the R (Red) to RG(Red with Green) down to the connector again J37>J36 where it turns R (Red) again Through the element other side where it goes to ground WB (white with black) and continues through the connector again until it gets to that body ground. That element is part of the circuit with the switch in the middle of it. both sides of the element are connected via the variable switch.

that switch has an LED in it and likely will never show as completely open as far as resistance goes. That entire circuit shouldn't get power until that relay is activated from the Blue IG source (10A) you see in the diagram. that 10A IG source just enables the 20A circuit to power the heaters. (This tells you what size fuze you should use here)

Do not use the same power on the IG side of the diagram as you get for the moving the seats as those are on all the time regardless of if your vehicle key is turned on or off (in most situations you can adjust the seats in a vehicle before you get in and even put in a key). You do not want your heated seats to be able to be turned on when the vehicle isn't running as people often forget to turn those off when they exit a vehicile.

I hope this helps.

in short the switch is between the Red and Brown and the black is your power in. as mentioned you can connect the red and brown and move the switch to either black or the white black (ground) wire but you will still want a relay that is triggered by the ACC at least to enable the ciruilt.

Thanks for all the info, and yes the seats will be on a ACC circuit as I also am worried about leaving them on. As far as what your recommending, are you suggesting a different wiring method then what I mentioned in my original post? As in if I supply power to B and BW and cross R and Br the heated seat should turn on and start to warm? I have supplied B and BW and crossed R and Br with no luck, the heated seats don't turn on. Or are you suggesting I move the switch to toggle/adjust the power being supplied to the B power wire? Sorry slightly confused. Will be doing more testing tomorrow night and hopefully some permanent wiring. I might post a video if I still have no luck after tomorrow

Thanks again, been wasting too much troubleshooting on this

 

[clx16]

Thanks for all the info, and yes the seats will be on a ACC circuit as I also am worried about leaving them on. As far as what your recommending, are you suggesting a different wiring method then what I mentioned in my original post? As in if I supply power to B and BW and cross R and Br the heated seat should turn on and start to warm? I have supplied B and BW and crossed R and Br with no luck, the heated seats don't turn on. Or are you suggesting I move the switch to toggle/adjust the power being supplied to the B power wire? Sorry slightly confused. Will be doing more testing tomorrow night and hopefully some permanent wiring. I might post a video if I still have no luck after tomorrow

Thanks again, been wasting too much troubleshooting on this

I am saying the idea you suggest could work however if you look at the diagram there are different places where red exists so being that I don't know where the harness was cut I can't be sure you are connecting the correct red to brown. Or the correct ground WB you think is for the heater vs the rest of the seat.