This write up is amazing. I ended up doing something similar, deflating the lumbar support all the way then innediately removing the power to the inflation motor, but it essentially made no difference. I'm considering doing what you did this weekend.So I ended up taking my driver's seat apart so I can see what was going on with the lumbar support. As some others have said in this thread, it seemed like the seats were more comfortable with no lumbar at delivery, and then, after playing around with the lumbar support, now it seems worse with more lumbar, and you're not able to fully deflate the lumbar as to what it was (no lumbar at all) at delivery.
In order to get at the innards of the seat, you have to remove the rear plastic clamshell cover. To remove this, you have to remove the headrest, as the chrome metal posts hold the clamshell cover in place. Although the headrest looks to not be removable, it is, and can be done rather simply. I followed this video below:
Basically, there's 2 metal clips on the left side of each post that you have to push and hold left, then once done, you can remove the headrest.
Once the headrest is removed, sitting in the back seat, put your fingers between the top of the back of the seat and the clamshell cover, then pull it out towards you. The bottom of the clamshell cover is kind of hinged at the bottom of the seat, so it'll just plop onto your legs.
Once this is opened, you can see the inside of the seat back, which includes a large yellow plastic piece. This piece has a air bladder inflator (grey metal box), which has several air tubes coming out of it...in my car, I had a green and a blue air tube. These are what inflates each of the air bladders, which are behind the yellow plastic piece. I was able to slide my hand from the top of the yellow plastic piece down between that and the seatback foam and feel the air bladders. They were fully deflated. To confirm the buttons were working correctly, I had my son press the top button, and the bottom button. The top and the bottom bladders inflated respectively. I then had him delfate them, and they deflated fully. Pressing the forward button appeared to inflate both bladders simultaneously. Again, by pressing the back button, both deflated as expected.
So my issue wasn't what I thought....that the bladders did not fully deflate. Nor was the issue that they fully deflated, then partially automatically inflated again.
It now appeared that the issue with my seat is that by default, it's designed with too much lumbar. I had to somehow reduce this.
I started out by pulling at the two slanted black metal rods that come from the top and go into the yellow plastic. They are pretty stiff, but I managed to reduce their tension on the seatback foam significantly; hence less pressure on my back. By sitting in the driver's seat before and then after, I noticed a bit of difference. Still, this didn't really affect the lumbar area too much, as the lumbar area is lower in the seat.
I then had my son put his hands on the left and right side of the yellow plastic piece about mid-way down, and pull it back towards him as much as he could. With me in the driver's seat, I finally found the seat perfectly comfortable !! Once he released, it was back to too much lumbar. So I needed to figure out a way to keep the pullback tension that he was doing to being permanent.
What I ended up doing was using some pink rigid foam insulation and putting it about mid-way down on both the left and the right side of the yellow plastic, taking note not to pinch the tubes on the right side. This keeps the yellow plastic further away from the seatback foam, and significantly reducing the lumbar pressure that it was putting against my back. I didn't notice any additional pressure coming from the left and right side as a result of inserting those small pink foam blocks. It doesn't completely eliminate the lumbar, but I'd say it reduced it by 90% or so.
I think ideally, if you'd be able to pull back the yellow plastic piece at the very bottom of the seat back, it would be perfect. But that piece seems to be installed quite sturdy to some heavy steel frame supports.
I included some pictures I took of the headrest removed, the seatback, the black rods before and after pulling them back, as well as the pink rigid foam supports I installed.
Let me know if you have any questions on this.
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Question - do you also find the actual seat to be uncomfortable as well? Specifically the side bolsters?