LH Seat Heater Switch (1 Viewer)

[TX FJ80]

I am in the closing stages of getting my interior back together after taking it completely apart to clean, change out all the bulbs, and rebuild my automatic climate unit and I’ve hit a snag.

The LH seat heater switch is acting funky.

The green Lo indicator is intermittently illuminating, seems to somehow fire back up when I change the rear heater switch position. It’s baffling me. I’ve now torn all of this back apart, exposed all of the seat heater and switch wiring, cleaned, greased, and snapped it all back together.

I’m still getting some flickering and intermittent behavior.

I know the relays and fuses are all onboard and factory - where are those relays? All I can think is:

1) defective switch
2) defective relay
3) bad ground
4) shorted wiring somewhere

Why does the rear heater switch position influence the LH seat heater operation? I looked for a wiring diagram and cannot find what I need.

Any help would be greatly appreciated!

PFA - only light in the interior that doesn’t work is the backlight for the LCD, but I hear that’s all too common and not an easy lift.

 

[TX FJ80]

So, here’s what I’ve done since encountering the issue.

Cleaned up the switches and connectors with QD Electronic Connector Cleaner and a pick, then re-greased and verified good connections and continuity in the switch harness.

Swapped switches - problem didn’t follow switch.

Then, after reading other posts for multiple hours and finally encountering detailed wiring diagrams and pin outs, I figured out how to isolate the problem.

I unbolted the driver’s seat and unplugged the seat from the harness going into the seat…problem goes away.

So, I have bad wiring, a short, and/or a failed component inside the seat/element itself.

Does anyone know how much life to expect from LCH ceramic heating elements?

Has anyone experienced something similar and how involved was the fix?

I’ve mentioned several times I’m wrapping up a refresh to get ready for sale, so I’m really not up for taking apart the seat - fingers and toes crossed it’s bad wiring that can be accessed under the seat.

 

[TX FJ80]

I de-pinned the connector so I had less assumptions and made the connections to the correct leads for the two heating elements (back and bottom).

When only the Lo circuit is hooked up, the Lo side lights up as expected. As soon as I tie in the Hi side I get both lights on the switch, as seen above.

At this point I am left with the idea that I have malfunctioning heater elements, which would require me taking my seats completely apart. Not worth it.

I’m super frustrated - this worked perfectly for the two winters I had the truck - now that I’m trying to redo to sell, it’s fail city.

Anyone been through this and anyone know of something I’m not considering that it might be besides something buried in the seat?