Seat Stuck All the Way Back
I had the same problem on my 1987 S4. The seat was all the way back,
power was getting to the motor, the motor was trying to move the seat
but no motion. The problem was a pinched cable between the bottom of
the seat and seat track. Moved the cable from the pinch point and the
seat worked. Hope this helps!
'87 S4 Black/Black
I just had the passenger seat of the 88 stick back (no go forward). I took the front cover off to reveal the motors/gears/spring drive shafts that cause movement. Try to determine which "corner" of the seat is sticking. Poke around and look ovet the mechanism and check the tracks for debris.
Created a special tool to turn the gears at the seat rail instead of trashing the spring drive deal. Basically a ratchet drive and 12" extension with a 1/4" (or just less) square drive. Jiggle it a bit and free up the stuck gear, be sure there are no dimes or screws in the tracks and reassemble.
This is the fix for the mechanical "stick". If you think the switch is OK (can hear the hum of the motor, but no go), then try this. Others have told you about the switch (easy, tear into it but don't lose parts!).
scad o 928s
Marc, et al... don't forget that there is a technical service bulletin on correcting a problem with the power seats getting stuck in the rearward position... it involves adding (I think) a new 'stop'. Dave Roberts also suggested that if you can hear the motor hum but get no movement: as you said, Marc, check that the rails are clear of "stuff" and then have some climb in the back and apply body force to the rear of the seat while you hold down the forward button. Again, this is assuming that you do have power getting to the motor.
1988 928 S4 A/T
If you have electric seats that are jammed but the motor still works (or tries to work), read this. This is one of those jobs that takes 30 minutes to figure out and 5 minutes to do. I hope that my explanation helps reduce the time.
Porsche Technical Bulletin #79003 December 1990
928 S4/GT electric seat jammed in backward stop position. Electric seat motor not powerful enough to pull seat from stop.
The stop washers on the seat rail threaded rod are modified (harder material) from production date June 5, 1990. The color of the new washer is white (previously light brown). Some of the washers on my '88 were black and some were dark reddish brown. The washers are about 3/4" in diameter and 1/4" thick.
The stop washers are not available as spare parts. If the seat is jammed in the backward stop position on earlier cars, cut the stop washers with a side cutter or similar tool (dykes) and discard.
Keep in mind that the rear stop washers are actually on the front part of the threaded rod, in front of the stationary nut that the threaded rod acts on. The forward stop washers on the drivers seat were missing on my car as though somebody tried to install the fix but cut off the wrong washers.
The method that I used on my '88 was to raise both the front and rear of the seat and put the seat almost all the way forward. I found that on my car if I hit the forward switch many times with the engine running (for higher voltage) it would come unstuck and finally move forward. If your seat wont go forward, Don't try to hand crank it with the "speed wrench," You will probably only break the plastic gear. Pull the cables out of the motor and try to free each side individually. There is a nut at each end of the shaft that imbeds itself in the stop washer and keeps the threaded rod from turning. As a last resort you may be able to cut the stop washer off with a knife.
It's hard to see under the seat and the stop washers are all the way forward on their threaded rods and you can't get to the stop washers from the front of the seat. Looking forward from behind the seat, look behind (to the rear) of the stationary nut, you can see what the front stop washers look like. They are identical to the rear stop washers (which are at the front). Reach under the seat and follow the threaded rod all the way to the front with your fingers. The washer will slide back on the rod with some effort. Pull it back almost to the stationary nut. You can see it now. Cut it off with your diagonal cutters. It is made of hard rubber. Do the same with the washer on the other threaded rod. Also do the other seat.
The TSB also says to move the seat at least five time against the backward stop position with someone sitting in the seat and if it still jams, replace the outer seat rail.
Left Seat Outer Rail: Part Number 928 521 489 08
Right Seat Outer Rail: Part Number 928 521 490 08
It is relatively easy to remove the stop washers yourself so it would probably be easier to do this job yourself rather than take it to a Porsche dealer. I don't know if this is a free fix or not but you could try Porsche. If you remove the washers and still have the problem it would be worth a try to have the Porsche dealer replace the seat rails.
Earl Gillstrom '88 S4 5-Speed
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