How to fix the seat motor?
 

We have a 1990 300E. The driver side seat motor is only moving forward. We are now squished uncomfortable.....Does anyone know if it can be adjusted manually?

you can replace the motor...

Check your connections first...
 

I recently had a similar problem with the driver's seat. I bought a new seat control since it is a very common problem, I still had problems, I bought a complete new (to me) seat and I still had problems. It turned out to be one of the female electrical connections between the seat and the car was too wide to make good contact with the male pin. There should be two electrical connections in the front under the seat. Try that first...In case that it is a bad motor and/or seat control, I may have all the parts you need. I can let go for cheap... Let me know and good luck.
P.S. Do a search, I posted some pictures recently...

Troubleshoot!
 

The seat adjuster switch is very failure prone, and should be the first item to check AND clean internally, followed by continuity between the door and the seat. Do any of the other directions work? Yes to the manual adjustment, you almost need the seat out of the car, this presuming the you have a power problem as I believe. You can jumper the motor at the connector and drive it back to a more usable setting.

Try running the seat FULL FORWARD until it stops. Then see if it'll move rearward. It should - had a similar problem with my W210 recently and this fixed it.