All switch parts disassembled.
First, 1st post, but y'all have helped me a lot in the past, so hopefully this can help someone. This is both a why it doesn't work and how to fix it. My specific issue was the "Up Temperature" button on passenger side, but it is problem/solution is relevant to the type of push button switch, that returns to normal position after releasing ( Temp Up/Down), not a toggle switch, e.g. (ETC Power/Snow). I started the car yesterday in So. Tx. and for some reason I reached over and to turn up passenger side temp a couple degrees for GF and once I pushed it in, it never returned to "out" position. Pic #1 The temp control just continued in rise in degrees until it was Max Heat, driver side was on Max Cold. I couldn't disengage Dual Zone, blah, blah, blah. (Disclaimer I didn't plan on posting anything, so the radio timestamp is actually after I corrected issue, but these were the Max Hot/Cold are the same indications I had.

The problem is the Silicone Rubber Button (I found out that's what they are called.) The button has a "conductive element" on the bottom of the button. These buttons have a resistance of approx. 55 Ohms. When the button is pushed, if the Climate CU receives a "signal" from the Passenger Temp Up circuit, it sends a signal to the Climate Control System to turn up temp on passenger side. Remember,since these are micro-processor circuits, they don't need a pure "0-5V Signal", all we need to do is pass enough current to trigger the semi-conductor. My understanding is, you can have up to 10K in resistance and still trigger ECU. My issue was, when I pushed the Temp Up, the silicone "sleeve" broke and the conductive material competed the circuit to the ECU that was telling it to turn up Passenger Temp, and since there was no way to remove that connectivity, it was sent to Heat Max.

Here was my fix. Remove defective Climate button. There are 2 metal clips, top and bottom, that secure it to dash board. I used a thin dental type pic, you probably need to reach an inch or so in to depress the metal tab. Carefully dislodge top of switch. Do same on the bottom. (Pic # 1 )

Disco the cable connector in the back. Remove metal tabs, and remove the "button shell" from the interworking's. (Pic # 2&3 )

You will see the thin 3 layer processor board. Top Layer is black silicone, with 3 buttons, the Middle layer is the actual green Printer Circuit Board, and finally the brown board that supports everything. (Pics #4)

You can see in my case the top button was defective. You can see the little conductive button in backgound. (Pic )

If you look at the PCB, you will see the 3 circular shapes that look like a finger point in something. The bottom is Temp Down, the top circuit is Temp Up. You can see from the PCB circuit trace that when continuity of current is completes the circuit to send signal to Climate Control Unit. (Pic 5)

I decided to utilize the "unused" middle button versus $115 on new switch. I carefully cut the top and middle buttons from the black silicone. IMPORTANT: Make sure you don't cut the silicone "legs/nubs", that go though the brown board. Make sure the middle button retains it's "leg" as we will just spin this around and use it as new Temp Up button.

(Tip, I tries to cut with Exacto, etc. Best thing is nip away using nail clippers. You'll see why when you do it.)

Carefully cut the middle position to fit top spot. (pic #6 )

Reassemble units, You can see Temp Up button is now in proper position. Works like a champ, I can adjust a required.

I'll upload pics shortly....they may not be numbered, but I'm burnt for day! You should be able to follow the general pic sequence and figure it out.

Let me know if you need clarification.

 

Pic#1 Max Cold / Max Hot


Pic #2 Release top and bottom clips


Pic # 3 Disconnect rear connector


Pic #4 Remove cover and found top button broken through. It is at top.


Pic #5 Completely disassembled


PIC #6 Circuit detail. Middle circuit is unused on Passenger Side only.


Pic #7 Carefully cut out bad button area


Top button removed, middle button repositioned.

 

Wow.. Excellent write up and great information. Good to have this in my pocket if/when they fail..

Thanks much!

 

Very well done Timmy! Great contribution!

Credit to you for wanting to troubleshoot & repair without simply buying a new button/assembly (part # is 87190-50020)

I would not have gone through the steps you took! I would have probably plunked down the ~$115 for the entire assembly! You saved yourself some nice money along with the self satisfaction of repairing it yourself! That's invaluable.

Excellent first post and intro to the 'club'!

 

Hello,
Thanks for all the info.. checked it out and all was good.

Similar issue but different... when temp is at cold... starts this way every morning... when I see it begin to ramp up.. I press either down button and it holds it in place... let go and it ramps up to hot... then it does not react to the down buttons at all....

Appreciate the help

 

I'm reviving this old thread to clarify: On my new 2020RX, when the green "DUAL" light is on, does that mean the driver's side temp control will control BOTH sides, or does it mean the driver's side does NOT control both sides? I think the issue is the definition of "on".

 

pages 75, 76, 77 https://drivers.lexus.com/t3Portal/d...f/OM0E025U.pdf