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7 Series Twisted Seat Back

By: Dave Walker <walker@boulder.nist.gov>

(If you'd like this emailed to you via within minutes, send a blank email to 750seat@mesaperformance.com)

This particular problem occured on a 1990 750iL, but the problem/fix is similar to most of the 7 series afflicted with a wayward seat.

The problem:

My wife was slightly reclined in the drivers seat and our 2 month old was crying in the back seat. She leaned back to see the baby and the seat clicked a little on one side. Now whenever we get in the car, the back of the seat is not even, the right side is further back than the left. Is there some kind of an adjustment that can be done without removing the seat?

The fix:

Classic problem, with fix described here more than once in the past, but I'll give it a go since I just finished fixing my dad's seat a couple months ago!

The problem has to do with the flexible cables which connect between the seat motors and the gear mechanism which effects the adjustment. The cable assemblies have an inner torque-transmitting braided metal cable with a plastic sleeve over them. Over time, the inner metal cable apparently shrinks under repeated torque applications until the (squared-off) ends retract out of the receptacle on either the motor or gear end. The solution is to shorten the plastic sleeve to compensate for this.

The procedure is to raise the seat up as high as possible to give yourself room to maneuver underneath. With the seat back, there's a single motor which has two cables coming out of it, one leading to each side of the seat back. When you adjust the seat back, one side moves and the other doesn't, so the non-moving side is the one you want to pull off. One hint: Be sure you adjust the seat back so that the two sides are even before you remove the offending cable. That makes it easy when you reconnect it to get the seat back straight.

Remove the cable at the motor end (underneath the front edge of the seat cushion). It's not real easy to do; I seem to recall I had to bend the piece of black sheet metal which holds the crimped silver metal end of the flex cable out a bit to get it out. Once you've got the cable end off the motor, pull out the inner metal cable and set it aside on a clean surface.

You now have two choices to shorten the plastic sleeve: (1) Remove the crimped end from the plastic, cut 1/4-3/8" (6-8 mm) off of it, and recrimp it *carefully*; or (2) cut the sleeve in the *middle*, remove a 6-8 mm piece, then reconnect it using a short piece of fuel hose and two hose clamps. I did the former procedure, but getting the crimped connector off is a bit of a pain, which is why some others have used (2). It's your choice, though.

When you've got the sleeve ready to go, slide the metal cable (add grease if it needs it) back inside, making sure the squared-off end engages the receiver on the other end. Twist it as you insert; you'll feel it when it's fully inserted and engaged. Slide the free end back into the motor. To make sure you get the inner cable engaged if it's not sliding in all the way, apply light pressure on the cable end while you nudge the seat back adjuster switch to turn the motor. When you've got it engaged (with the seat back straight!), bend the retainer back to hold it in. Try out the seat controls to ensure it's working properly.

It's up to you if you want to go ahead and do the other cable, which probably isn't too far behind the first in the steady advancement towards failure. While I was in the mood, I fixed the two headrest height adjusters as well. This requires removal of the seat back to get to the cable, which is simple: pull up on the bottom and it pops right off. Total time-of-repair for four cables was about 1.5 hours, including the 1/2 hour of bungling about for tools, flashlight, etc., which always preceeds my getting down to doing the real job.

Dave Walker