"Le meilleur et le pire." Paraphrasing Dickens through Victor Hugo.

So, it goes like this....

I knew the passenger seat was not working and the fuses were working. Since the seat controls were also broken, the forums told me how to move the seat so I could get it out with the rather prominent connector just to the front of the seat module. Simply apply 12 V with a car battery, first with one polarity and then with the other and the seat will move into the appropriate position to remove. It appears quite difficult to remove the seat if you don't do this, and there is evidence a previous owner tried to get at the bolts "from the top" as it were.

In any case, I went ahead and fixed the headrest problem. Having not seen an operating headrest in the six I have, it's unclear to me 1. why this went on for so many years, 2. how any of them worked for very long.

But, no matter. Back to the seat controls and the seating module. So, a quick perusal of the wiring diagram suggested that
1. If I simply bridged pins 9 (brown wire) and either 6 (blue-yellow) or 13 (orange-yellow) on the control connector (SP11), then the seat would move forward and backward if the seat module worked. Did this and nothing happened.
2. I could check to see if the headrest worked on a different module by bridging 9 and either 14 (down orange-green) or 15 (up brown-green), and the lumbar support operation. Did this and the gratifying up and down motion of repaired headrest resulted. This basically confirms power is going to the seat.

Now, we could pretend that I had done 2 by simply looking at the wiring diagram and realizing the implications of the headrest motion, ignoring the fact that I pulled the other seat that was working (driver side) and checked the power going to the seat, how the seat controls worked and confirmed everything on the passenger side before realizing that the headrest going up and down meant that I pretty much didn't need to do any of that.

So, at this point, it looks like a module problem (maybe a wiring problem, but since module is common, I assumed module). I pulled the module, opened the box without breaking any tabs, and looked at the passenger side board. Looked like the passenger module picture below.

The board looked better than every one I've seen posted here, Since there wasn't anything particularly obvious, I started checking resistances between the working ends of the edge traces and found one microscopic short. I bridged the two components with a 34 gauge wire and put the module back on to try, see below. Worked great, success. Best of times. The passenger seat traversed back and forward, leaned forward and back, headrest and lumbar functioned. Put the passenger seat back in and went to the driver's side to re-bolt the driver's seat.

While I was playing with the driver's seat, I had left it in a far forward tilted position. Don't do this. Because when the seat quits working, and you may need to move the car because the door is too close to the garage wall, It's hard to drive with the seat tilted far forward.

I mentioned that the seat stopped working. While I was trying to move the seat backwards to get to the front bolt locations, it stopped, dead. Fuses were great. No obvious pulled wire. Rest of the car looked fine, passenger seat still worked. What the hell?

Disheartened by suggestions that it was a programming and compatibility issue with the new module after the previous success, I left the car overnight.

In the morning, cleverly, I reasoned that since I could easily swap modules, I should do that, since it would allow me to move the car without new articulations in my spine. That worked great.

Later, round 2, open the driver's module. Worst of times. The module, which had been working up until I decided to work on the passenger seat, looked like crap. It's not clear how it was working at all. See below

In any case, I started checking resistances and inexplicably found only two traces that looked like they were shorted, perhaps from a thinned wire explosively evaporating under larger current than possible for the now tiny conductive path. Bridged the two sets of components and tried again. Didn't work. Wasn't clear why since everything else seemed okay, electrically. After much muttering, I went and bridged everything that connected an IC to a relay that had a trace that went past the edge of the board, since that portion looked worse than it appeared to be electrically. Since there were touchy and tiny connections right to the IC that fed the relays, I 'enhanced' the board with epoxy to strengthen those locations. I did not epoxy the edge of the board, the likely source of the humidity/water intrusion that led to the corrosion. It's not clear that will stop anything.

To make a long story even longer, that worked, best of times again. Moral of this story, the seat module is likely repairable, no matter how crappy it looks.

And thus ends a tale of two modules. No one died at the guillotine, and no one had to endure Dickens.


Passenger module picture, looks fairly good, one microscopic short


Repaired passenger board with one bridged trace


Driver module picture, previously functioning until it became jealous that I had fixed the passenger module and gave up the ghost spectacularly. Or 'how the hell did this work in the first place' 1.


Driver module picture, previously functioning until it became jealous that I had fixed the passenger module and gave up the ghost spectacularly. Or 'how the hell did this work in the first place' 2.


Top side of repaired driver module with multicolored bridged traces. Not as elegant as the passenger board, but more entertaining


Bottom side of repaired driver module with multicolored bridged traces. Not as elegant as the passenger board, but more entertaining

 

Good catch, and well done....