Hi there.
I tried knocking the motor with no result. I can't really put power to it just to test the motor because the seat is stuck in the very back position and I can't remove it. If I just undo the bolt in the front and force it to lift in the front I will just end up bending the rails. That will be another issue.
OK Success
I did not explain very well in my last post so will try again.
First of all my car is a 2003 4200 right hand drive spyder. So it may not work in other models.
This for the back and forward movement on the seat
Looking under the seat on the left is the motor with a white tube coming out of the front and going into the right hand side rail.
In this white tube is actually a drive shaft, the motor turns the shaft and in turn drives the cogs in the side rail that moves the seat.
The motor is held on with 2 T20 torx Screws you will need a long handled driver to get to them Right hand screw is easy to get too. Left one is at an angle but you can bend the motor/bracket to get to it.
The power cable is attached to the motor and I switched off the battery and just cut it as I could not get to the connector (can be sorted once the seat is out)
I just pulled the white tube/drive shaft out of the motor and attached my drill to the end so that the drill turns the shaft and in turn moves the seat!!!
Make sure the shaft is fully in the white tube if it is pulled out too much it wont engage with the side rail cog