'93 850 seat back mechanism problem

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:
http://www.volvospeed.com/Repair/seatcable1.htm

Reason for my posting, is that I have found a couple ways to "shortcut" the
process if you are not willing to go all the way by peeling the seat cover
all the way up and actually replacing the cable (which is the right way to
do it).

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.

1. 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.

2. 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

 

<snip>
An alternative is to heat the ferrule with a butane lighter and pull it
off the cable housing. Snip the housing back about 3/8". Use a 6mm deep
socket to drive the ferrule back on the cable housing. The square drive
should now protrude from the end of the ferrule. Slide the ferrule back
into the gear drive, swing the latch plate back over the ferrule and
test. It should work as good or better than new. The plastic housing
stretches over time, especially if larger bodied people use the seat. The
cable routing is quite close to the upholstery padding and gets stretched
through normal use.

Bob

 

Excellent - thank you for the idea. I couldn't for the life of me figure
out why the doggoned cable inside the sheath would become shorter. Your
explanation says it all - the sheath itself stretches instead. Amazing that
this would happen. A cable sheath obviously should not stretch like that.

Regards,

Mike

 

Well cheesy is as cheesy does. That plastic sheath probably costs a
tenth what a wire wound plastic covered cable sheath would cost.

Bob

 

The cable sheath is just plastic tubing. The metal ends are merely
crimped on, and have a tendency to work loose:
http://webpages.charter.net/dwarner2/cable.jpg
I bought a new cable for mine, but once I figured out what happened, I
heated the ends a bit and pushed them back on. It's been holding up
for about 2 years now, but then, I probably adjust the seat back less
than once a month.

You want the intter cable to stick out about 10MM with the other end
flush with the metal end.

I'll second the recommendation of using cable ties along the bottom.
It's next to impossible to get hog ring pliers in there. )When the
seat back was originally covered, it wasn't attached to the seat. )

Also, if anyone is contemplating doing this, get a good, heavy pair of
diagonal cutters. My old blue-handled ones would't make a dent in
the hog rings, while a decent Klein pair nipped through them like
butter.



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