I suppose any good researcher has to report his failures as well as his successes, so.... You may have read my post about the mechanism that raises and lowers the drivers seat, or more to the point, did not do so. I was able in that first experiment to manually adjust the seat so it was almost correct. But... I wanted it to work!
Small problem: the gearbox (which would not turn but about three-quarters of a revolution) is not a service part. That means you have to buy the assembly that it is part of, instead. In this case, that assembly was the entire seat base for nearly $1000!
A few days later, I found a used Z3 seat on Craigslist for $100. The owner told me that the upholstery was shot, but all I wanted was the base anyway. I bought it, brought it home, and eagerly tried it, only to find the gearbox on this one would not turn at all! Drat. Must be a common Z3 problem.
Since I had this dead seat to play with, I drilled out the pin holding the gearbox in (which is a destructive, non-reversible procedure), and examined it. Four torx T20 screws held it together, and when I removed them, I found that the problem was simply solidified grease. I cleaned it and added new molybdenum grease, and it turned fine.
Great! Now I had a part to repair my seat - all I needed was a relatively non-destructive way to get my gearbox apart, so I could replace the "nose" of my gearbox with the one from the dead seat. I needed to get to those four torx screws. Unfortunately, here's the view of those screws:
Yep, they are buried under that solid bracket. I had decided while working on the dead seat that I could drill access holes in that solid bracket, and remove the four screws that way. The first problem: my cheap consumer-grade drill with a keyless chuck would not hold the drill bit tightly enough to drill through that thick bracket without spinning the bit in the chuck. Fortunately, I still have this:
I think my Dad gave me this many years ago, with a bad cord. I replaced the cord (before we left Texas, so it was 1986 or prior) and it has worked fine ever since. Since it has an old-fashioned chuck with a key, I could use a hammer to REALLY tighten that bit, which did the trick.
I drilled four access holes, more or less guessing where to put them. If you are going to try this at home, the two lower holes should be a little more "outboard." But it was good enough, and I got the gearbox apart.
What I found is exactly what I expected, given the failure mode - broken teeth on the plastic gear. Who builds a non-replaceable gearbox with plastic gears? Grrrrr!
So, I grabbed my replacement gearbox nose, and... it wouldn't fit. See, I assumed that the gearbox would be the same on the driver seat in my car, and the dead passenger seat I bought, but NOOOOOO.... those crafty Germans build unique, mirror-image gearboxes for left and right.
Well, while it was out, at least I adjusted my seat a little differently, so it now does feel exactly where I want it. And, when my passenger seat dies with same failure, I already have the part to fix it.
If I ever meet the German engineer that designed that failure-prone, non-repairable part, I'm going to tell him, "Ich bin zu Ihnen in den Knöchel kick!"
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