Installing seat heaters + wiring question (1 Viewer)

[drowzyGX]

My driver's seat has no heat, regardless of the setting on the switch. My passenger seat has full heat but no adjustments. Illumination works on both seats.

Prior to buying new OEM switches, I want to ensure I'm testing everything correctly.

I get the following results on both switches

• 5 <-> 6: continuity regardless of switch setting
• 1 <-> 3: no continuity
• 3 <-> 4: continuity at every setting of switch except off
• 2 <-> 3: no continuity at any setting on switch

For the driver side, I'd expect to get heat but no adjustment like the passenger side. Since I'm getting continuity between 3 <-> 4, this should be enough for me to test the harnesses in the seat, yeah?

Any thoughts why I only get heat on the seat bottoms? Is anyone getting heat to the seat backs?

Finally, does anyone have a wiring diagram for the harness that these plugs go into? My center diff lock works, but I get inconsistent backlighting (green light). It comes and goes with wiggling the switch. I get continuity when pressing the diff lock button (as expected) and the switch works when plugged in.

 

[drowzyGX]

Opened up the seat heater switch today to do more testing with the multimeter.

As the adjuster is clicked on and then increased to max power, the 3 metal tabs make contact with the 2 metal strips and the black strip on the circuit board to complete the circuit.

I tried sliding that metal piece by hand and measuring resistance. Same result: only getting a circuit on pins 3 and 4, nothing on 2 and 3.

This thing seems so simple that it should be able to be rehabbed without buying a new switch, but I’m at a bit of a loss. New to electrical work.

If anyone has advice for next steps, I’m all ears.

 

[Rednexus]

You can probably find a used switch on eBay for around $20-30. They are shared with lots of other Toyotas, so it's probably the same switch as a 4Runner or Highlander of the same era. I'd source a good used one, or see how much a good new one is from somewhere like Partsouq, rather than paying $$$ for one from the dealer.

For the lighting problems, the green backlights in the switches really like to burn out after 15+ years. I had to replace *every*single*one* of mine. Full LED bulb/socket replacements are the easiest option. But they are brighter than stock, and they don't dim quite like the OEM bulbs do. I tried to use OEM bulb replacements but had a real hard time even finding the right sized bulbs.

https://www.amazon.com/gp/product/B07J52V55X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

I also replaced some of mine with these, it was just a lot harder as you need to carefully extract the old bulb from the socket, put in a new one, and snip the ends of the bulbs. I'd recommend the option above instead for simplicity.

https://www.amazon.com/gp/product/B074SY1KP5/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

 

[drowzyGX]

I ended up disassembling the center diff lock switch and cleaning the contacts with MAF cleaner. That plus a known working bulb stopped the issue with flickering. So that's one switch and one problem solved.

I didn't want to chance used switches that likely weren't tested for continuity per the FSM, and I didn't want to pay dealer prices. So I ordered new seat heater switches from partsouq.

I've got both seats out and in my office. I'll likely end up replacing some of the heater elements or at least rebuilding wiring harnesses. My passenger side seat failed one of the continuity tests for the harnesses that handle the setback heating. Passenger side passed the voltage checks for the switch being on full blast.

Driver side harness looks shot because it didn't pass any of the tests, even after swapping the internals of the good passenger switch to the driver side switch body.

Should make for a decent project while on PTO over the next week or two.

Wondering if I could replace the plugs on the harnesses and use the Toyota rocker style lo - hi seat heater switches from the FJ80. The rotary one seems more prone to failure.

 

[drowzyGX]

Seat tear down complete. Definitely an issue with the heating pad.

Any thoughts what that black thing is on the right that connects the two brown wires?

Those wires are supposed to have continuity, but they do not. That black thing is the only object between them.

The black box on the left is good, I think. The two wires that feed it have continuity between them.

I do NOT have continuity between the red power wire and the black wire in the bottom of the picture. These are the two wires that connect to the either end of the copper heating element.

Really would like to be able to repair this as a replacement pad is like $200 on eBay or $500 new…and that’s just for the seat bottom.

If a repair isn’t possible…would it be possible to hook an aftermarket heater to the factory harness?

The heaters I’ve looked at need:

• 12v 10amp source
• Ignition source

The harness the factory switch plugs into should have this, yeah?

 

[Rednexus]

The black box does not appear to be listed in the FSM. If it were my rig I'd pop it open and see what it inside and if there is possibly a broken connection or other obvious issue inside it that could be easily fix/re-soldered etc.

Regarding aftermarket heaters, I'd personally see if they could be ran off the OEM switches and wiring. In theory, they should all be just providing +12V to the seat heaters. You'd need to plug the system back in and see what pins in the connectors get you +12V and a ground and how that changes with switch operation. I'm not sure how the heat is modulated - such as if operating the switch changes the voltage, or something else. Your multimeter should help tell you how the system works.

If it's not feasible to run them off the OEM harness, you can pretty easily bypass the OEM system via fuse taps into the panel that's under the driver's side dash. This would avoid splicing into the OEM system and would be removable if you ever wanted to go back to stock. A 12V 10A source would be the power seat fuse, which is always hot. I'm pretty sure the ACC/cigarette lighter circuit is hot only when the ignition is on, which would get you the ignition trigger the aftermarket system needs.

 

[drowzyGX]

So that black box is, I believe, a thermostat. I found a parts diagram for an LX that has the thermostat in the same spot. I will snag a month of access to that TIS website this week to confirm if that’s the case for the GX.

I think the box is fine because it’s at least got continuity when checking the wires that flow to it / from it. I’ve got continuity issues everywhere else though, lol.

The troubleshooting guide for the seat (one of the few sections I’ve got downloaded) has the voltage measurements for the wires and each setting of the switch. My issue is I don’t have a fully working switch at the moment. They’re on the way from partsouq.

Fingers crossed I can simply re-pin some of the plugs in the harness on the seat, and use that with an aftermarket heater and the oem switches.

Good to know about the power seat fuse. That seems like an easy solve if trying to stick oem proves too difficult.

Will probably go ahead and order new bottom seat leather since mine is worn out, and it’s already removed.

 

[Rednexus]

Here is the link to the full 2005 GX470 TechInfo:

https://lexusgxor.com/_media/general:2005_gx470_techinfo.pdf

 

[drowzyGX]

Here is the link to the full 2005 GX470 TechInfo:

https://lexusgxor.com/_media/general:2005_gx470_techinfo.pdf

I am truly embarrassed that I’ve been on this forum over 4 years and did not know the Gxor site had that fsm, lol.

Thank you for sharing. Merry Christmas!

 

[Rednexus]

I am truly embarrassed that I’ve been on this forum over 4 years and did not know the Gxor site had that fsm, lol.

Thank you for sharing. Merry Christmas!

No problem! It's saved my bacon a number of times. Hope you have warm seats for Christmas!

 

[drowzyGX]

UPDATE

Purchased these aftermarket, but made-for-Toyota seat heaters (250-1870-TOY). They come with a dial switch like OEM, but the switches are slightly different in size. They do not fit into the OEM spot.

Both the OEM and aftermarket switches have 6 pins out to the wiring harness. I would like to use the OEM switch with this harness.

Question
Is the right way to test feasibility, to measure voltage at each pin on each harness with the ignition on and: switch off, switch low, and switch high?

left to right in picture	Ignition on, switch no power	ignition on, switch low power	ignition on, switch max power
(6) green	7.1 mV	7.1 mV	7.1 mV
(5) black & white	7.1 mV	7.1 mV	7.1 mV
(4) red & green	0	13.7 V	13.7 V
(3) light blue & blue	13.7 V	13.7 V	13.7 V
(2) red	0	13.7 V	13.7 V
(1) black & white	0	0	0

I believe 1 & 2 are the circuit for the button illumination. They match those pins on the switch testing guide in the FSM.

I think I want to temporarily wire up the aftermarket heater and measure voltage at each pin in the switch harness. Then I could de-pin the aftermarket harness and re-pin it to use the OEM switch.

Thoughts?

 

[Rednexus]

I think you would want to also do a mock hookup with the aftermarket harness and see if you can match the pins between the swtiches. if that is possible, you'd simply cut the connector off the OEM switch and then splice it into the aftermarket harness. The OEM switch might also work by changing the resistance between two of the contacts as the switch moves - so I'd also check the FSM and see if that is the case, and then see if the aftermarket switch works the same way.

Caveat: I've never done this before, that's just how I would attach it to try and get it to work. if the OEM and aftermarket switches don't work the same way, it might not be possible.

If all else fails, you could see if Blue Dog could make you a switch panel that has the smaller Toyota size aftermarket switch blanks in it. He made two custom panels for me.

 

[drowzyGX]

Won’t be able to use the OEM switches. That’s a bummer.

The 6 wires on the aftermarket switch all have under 7V when the heater is powered on. There’s a box on the aftermarket harness, and the input power, switch wires, and wires to the heating pads al connect. Guessing this box handles all the magic, and that’s why the switches don’t match up.

Thinking I’ll have to reach out to blue dog or someone else to either print a new plate or an adapter that goes in to the oem switch slot and lets the aftermarket switch plug into it.

Wondering if I can take only the heating pads and splice them into the factory harness somehow? I’ll check voltages and such.

 

[drowzyGX]

Installed the heaters and replaced the seat bottom cover. Now that I know how easy this is, I may go ahead and replace the seat back leather for the driver seat and install new seat heaters in the passenger seat.

Parts
Seat heater: Rostra 250-1870-TOY ($130)
GXARTS seat bottom ($50)

Removing the seat and the factory leather was a pain. Installing the new heater pads, and putting the leather back on was a much faster process.

The new cover isn’t leather, and it doesn’t match perfectly. This is a 20 year old car, and I’m not gonna complain for $50.

Gonna re-install the seat tomorrow. The harness is already wired in the car.

In contact with Blue Dog Designwerks to get the 3D-printed ashtray switch panel with custom cutouts to fit the switches for the seat heater. I’ll leave the factory switches in place.

Install process:

 

[Rednexus]

Looks great and glad you'll have warm seats again! After reading your thread, I've been paranoid about my seat heaters not working. They're just taking a long time to get warm it seems . Got spoiled by our old Subaru which had toasty seats in a minute - as well as toasty HVAC heat in a couple minutes. Toyotas (and most other cars) just don't get warm as fast.

FYI for your un-used seat heater switches, you can always put stuff in their place like accessory switches or a USB quick-charger. Quite a few things are made that fit the large Toyota switch blanks.