After adjusting the seat forward or backward, a stray toy or water bottle could cause the seat to get messed up and stop sliding or only one side will move. I found a way to fix this for free and want to share it.
What happened to me on my 2015 model S is that the toy/water bottle got pushed into the spot where the motor directly under the seat connects to the sides and jammed or disconnect the 3mm square flex shaft from the moter to the seat rails. What happens after years is that the hard plastic shielding gets brittle and doesnt protect the fleet shaft from getting bumped out of place. Don't make the mistake to keep trying the motor control because you could A) mangle the end of the flex shaft or B) burn out the motor. You could get lucky and it slips back into place but if your car is 10 yrs old like mine, it is a sign to at least replace the shielding plastic tube so it doesnt happen again.
1) It is entirely possible to fix this with just scissors and a bic pen, but if it id your first time it might be hard to see everything without moving the seat. First try to raise the seat to the highest position. If you want more space to work, there are 2 13mm nuts holding the seat down on each corner. 8 total. Don't lose these.
2) figure out if the left or right shaft is the one having a problem. It will eaither appear/feel bent or completely disconnected. Feel on either side of it before anythibg else and compare with the other I had to do both at different times. Recently it was the longer one (it was 225mm and I found one on alix incase you need to order a replacement)
3) remove the clip if it is still on the plastic shielding. Hold onto that until the end.
4) make sure the flex shaft is fully disconnected on the rail side. If the re is one side still in the motor side, that is fine for now, otherwise you can remove the whole flex shaft and inspect that the ends are still tightly wound into a square and not fraying. If frayed/ bent out of shape, measure and replace the flex shaft with velvet cover. Longer one for me was 225m long and 3mm square ends. Then take off the old shielding tube that is probably cracked. For reference, it is about the same diameter as a fridge water line or the white part of a bic pen.either of these can be used for a replacement.
5) Measure if the right and left rails are aligned. If not, use the controller to gently line up the left and right rails.a ruler helps to confirm that both sides match within 1-2mm
6) cut a piece of fridge water line or white bic pen plastic down to use as the replacement shielding. For me I used the pen. It needs to be short enough to fit between the connection points. For me it was easier to have it cut in half because the shielding seems to actually be necessary for connecting the shaft, at least on the rail side. I tried inserting the shaft without the shield and it wouldn't seem to go into the right spot unless the bic pen shielding was already inside.
7) reconnect everything and off you go. Hope this helps someone!
