I, like a lot of other '93 850 owners, have had their driver's side seat-back mechanism fail (the known cable problem). The motor runs, but the seatback does not move.
The Bay13 website has a superbly documented procedure for replacing the faulty cable. It is also very well illustrated:
Before you start anything, I'd recommend (like I did) printing out the Bay
13 article (in color if you can) and bringing it with you to the car with your toolkit so you have it on-hand as you progress.I will admit that my laziness (and time frame - it was new year's eve) kept me from completing the job by actually replacing the cable, but here's what I did. First, I only peeled back the seat cover enough so that I could get to the four screws and the shaft retaining clip. I used an extra long phillips screwdriver. Essentially, I removed the switch assembly (per Bay
13), and clipped the 4 hog rings along the bottom of the seatcover where they meet from the front and rear. I also undid the seatcover from underneath the left side. I rolled up the rear of the seatcover just far enough on the left side to expose the gear assembly, a few inches of cable, and the left half of the square metal rod. I bunched up the seatback and held it up with a bungee cord around the headrest. Make sure you don't pull the seatback fabric to hard or you'll tear it away from the RIGHT bottom side, where it's still in place. I started to actually tear mine as I was peeling up the left side, so I took it easy after that.
- As explained in the Bay 13 article, disassemble the left-side gearing cover (4 screws) and shaft retaining ring. Remove the end of the cable carefully. It will be greasy on the inside. Once I pulled the drive cable away from the gear housing and looked into the end of the cable, the cable itself (the square metal springy thing inside the sheath and housing) was FLUSH with the end of the metal fitting on the cable. That seemed odd to me - as it did not appear broken, but only recessed into the metal cable fitting. Thus, the square cable was not engaged into the square socket at the top of the worm gear assembly (the worm gear is that helix-shaped white plastic gear you see in the gearing assembly). So when you run the motor, nothing happens since the square cable is up inside it's housing instead of being socketed into the worm gear like it's supposed to be. I don't know how the cable works it's way back into the cable housing, but that appears to be what happens over time. So anyway, I ran the seatback motor with the switch, and sure enough I could see the cable spinning inside the housing as you'd expect - except that it's recessed - and that's the problem. With a pair of needle nose pliers, I was able to pull the greased cable out of it's housing an inch or two. Then of course running the motor again it would NOT spin (I pulled it out too far, so it disengaged from the motor end). I pushed it back in, but left about 1/8" to 1/4" sticking out. I ran the motor, and it would spin just fine again, except with the bit of cable sticking OUT the end of the housing now (like it should be). So, I socketed the cable back into the worm gearing, with the square cable itself socketing OK into the top of the worm gear assembly. Screwed the gearing cover back on, put the retaining ring on the shaft, and the seatback works fine now. Perhaps at one of the two ends of the cable, there is a retainer of some sort that has broken or worn away, allowing the cable to slowly work it's way back into the cable's sheath, thus disabling the ability for it to turn the worm gear, which in turn is supposed to run the gears to move the seatback. I imagine at some point in time, if I use the seatback adjustment regularly, that the cable core will again creep back into it's sheath, and it will again stop working. A retainer somewhere in the cable/motor assembly is probably worn or broken, thus allowing the cable itself to move back into the cable sheath. That's all I can figure.
I do not know how or why the cable itself works its way out of the worm gear and becomes recessed into the cable housing, however this fix at least let me re-set the seat back to the position it always has been for me (and make note of the clever motor recalibration "nudge" trick described at the end of the Bay 13 article). I am the only one who drives the car, so it's no big deal that I set it and forget it. The problem was that a few weeks ago my wife took the car to work, and she moved the seatback for her own comfort, and sheer coincidence - the seatback stopped working at that very moment, in a position that was uncomfortable for me (DRAT). So that's how it originally happened, and now it's fixed again, without having to go all the way to actually replacing the cable. The only thing still unknown is what has happened with the cable that over time it will appear to recede back into it's housing, on the gear assembly end? Does anyone know why this happens? Is there a fix on the cable, instead of buying a whole NEW cable? I can imagine it being something on the motor end that has failed (like a retainer) that would normally keep the cable in place, and NOT move in/out of the sheath.
- The second thing I think you could do if you don't really adjust the seatback much (i.e., you're the only one who drives it), and don't feel like going all the way to replacing the cable, is to use an 8mm open-end wrench to turn the square metal bar that goes across from the gear housing to the other side of the seat (the left side of the square bar is exposed). I discovered that I could turn it by hand with that 8mm wrench and it would turn and the seat back would go backwards manually. This works just like the passenger side where you turn a knob to adjust the seatback. Problem is, I WAS NOT able to turn the shaft the other way, to make the seatback go FORWARD (because it would bind due the worm gear, no surprise). You could probably disassemble the gearing as per the Bay 13 article and remove JUST the worm gear (leaving the cable where it is). This will free up the gearing to allow you to adjust the seatback up and down using just the 8mm wrench, manually, from under the seat back. There are certainly drawbacks to this so be aware:
- The motor still will not make the seatback work (since the worm gear has been removed, even if the cable was not faulty).
- I did not actually do this (remove the worm gear) so I don't really know if the seatback will "creep" backwards over time without the worm gear no longer there to keep it from doing that. You could rig something perhaps to keep the square bar from turning, but it would be a temporary measure.
- You would have to keep the seat cover undone so you could continue to access the square bar from the back with your 8mm wrench whenever you need to adjust the seatback. Hang onto the worm gear if you remove it - you'll need to put it back if you decide to actually replace the cable in the future.
So that solution is a bit wonky, but it would at least allow you to adjust your seatback by hand with a wrench, until such time you decide to go whole-hog and actually replace the cable as described in the Bay 13 article.
Ultimately, your best bet is of course to replace the cable. In my case, I found I was able to pull the cable core out a little bit to engage it back into the worm gear and that was the fix I did. I used the nylon zipties to put the seatcover back together at the bottom (the Bay 13 repair calls for metal hog rings, which would be the "right" fix, but it does also mention some people using zip ties, which I did). BTW I found the best way to do the ziptie truck is to force a needle nose pliers down from the top of the BOTTOM seatcover flap thru the original hog ring hole, and pull the end of the ziptie up from there. Do that for all four places where the hog rings were originally. I suppose sturdy tweezers would work too. Then, do same for the ziptie pulling each thru the original hog ring holes on the upper seatcover flap. Then you just connect each of your zipties in a loop and pull, kind of like sewing with zipties. This pulls the seatcover bottoms back together nicely, with the wire rods offering nice support.
So that's my new year's eve seatback repair saga. I hope it helps someone else.
Finally, I'd like to thank the folks at Volvospeed for their EXCELLENT Bay
13 fix/modify instructions on a variety of Volvo related issues. I have used it many times to fix/modify known 850 problems, on my '93.Mike