I've read tech's post with the step-by-step guide for repairing the 850 seat back cable (great write up!). I suspect this is what I need to do for my car but before I dive in I wanted to ask about my specific situation. The seat will go up and down, but only one side moves. That is, when the recline button is pressed, the right side will recline but the left side stays stationary.

Is this one of the common modes of failure? Maybe the cable is held up on something so it's only pulling one side? The pictures in the guide are great but I'm having trouble figuring out how only one side would bind like this.

 

That is not a common problem.
But you will have to get in there to look it over. Someone might have been in there before and didn't connect something properly.

 

OK, thanks. I'll check it out at some point. Maybe I'll get lucky and the hinge is just binding on something.

 

I wanted to follow up on this in case any other members run into this problem and try to search for information on it. I was unable to find any other references to this problem on any of the forums I've been to, and via google searches. So, presumably it's not a common problem.

EDIT: Multiple posts to cope with forum problems.

 

Here's a picture of the full seat back with the leather removed:

 

That's a picture of the left side mechanism in my girlfriend's 1993 850. If you look closely you can probably tell that the rod is not actually inside the square hole in the gear mechanism, although in that photo it happens to be aligned nicely with the hole. The rod had somehow come out of the hole on the left side and been pushed further in on the right side.

 

I Sprayed some WD-40 into the gear hole on the right side and into the hole where the rod goes through the transmission.

 

Using a combination of the motor, manual pressure to move the rod, and sticking a flathead screwdriver in the hole to manually move the left side of the seatback up and down, I aligned the rod with the hole and pushed it in from the right side of the seat using a screwdriver.

 

The above only got the rod into the hole a few millimeters. To finish the job, clamped some vise-grips onto the rod and banged them to the left with a hammer. This got the rod firmly centered between the right and left side gear mechanisms.

That's all there was to it!