Well, after over two hours of struggling with the upholstery (the valleys are held down with plastic rods sewn to the outer skin, linked to steel rods embedded in the foam by wire rings that aren't quite hog rings, and aren't quite split-rings, but are an unhappy combination of their worst features), and five minutes of jury-rigging the kit harness to a lighter plug, I now have a heated driver's seat.
Before doing anything else, I disconnected the 12V battery, and let it sit, while I checked my email, did some record-keeping, and had lunch. About 40 minutes later, I started unbolting the seat. I broke the bolts loose with a torque wrench, so that I'd have a number to shoot for when reinstalling: 30 pound-feet.
I really don't think they could have made that seat any harder to work on if they'd tried. There are three valleys in the bottom, each with four of those miserable wire rings holding the plastic rod down, and barely -- BARELY -- enough space for one of the heating elements to go in and lie reasonably flat. I had to open up ten of those rings (four in the front, and the front three on either side), in order to peel back enough of the fabric to get the heating element in, and then hook them back over the rods and close them back up after it was in place. And there wasn't any convenient place to route the cable: I had to poke a hole in the foam, Gorilla-tape the plug onto the female end of a socket extension, and pull hard to get it through to the underside.
The back only had two valleys, and it was only necessary to open up one of them, the inboard side. Which is really good, because on the outboard side, the side-curtain airbag is attached to the outer skin. (I will note that there's also a tag attached near the breakaway stitching: do not re-sew this cover.)
On the bright side, the valleys should keep the heating elements from doing any migrating.
Once I had everything back together, I hooked up the wiring and bolted the seat back in, torquing the bolts back to 30, and reconnected the 12V battery. After nearly 3 hours of no 12V, all I had to do was reset my radio presets (all two stations: KNX for all six AM presets, and KUSC for all twelve FM presets) turn the charge timer back on, and reset the default dashboard display to the big state-of-charge indicator.
Then, with the lighter plug that I know I have lying around somewhere completely buried, I went over to O'Reilly for another one. It took me all of five minutes to jury-rig it to the kit harness, and verify that the heaters work as well in the car as they did when I bench-tested them. This will do, until I've built my own control mechanism (and yes, I now have a small stock of 74LS76 dual JK flip-flops and 2N2222 transistors, as well as some relays to handle the roughly 5A the heating elements draw.
And I did it without the side-curtain airbag blowing up in my face.
James H. H. Lampert