If you can hear the motor run but the seat will not move then the drive cable has disengaged from the motor, its a pretty bad design as it does not employ a positive stop and the cable can move in and out of its sheath.

You can either shorten the sheath of the cable for a permanent repair - just resetting the cable works also. My car also faced that problem, I took the seat out and fixed it.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)