Power seat will go back and forward but upper seat won't. Can hear the motor in the seat running.

Question edited for clarity, you forgot Herr. Benz.
Question moved from Spanish Car maker category Seat, (pronounced See-At) and nothing to do with car seats.

Can you hear the motor running? It can only be 5 things

Fuses
The Switch
The Motor
The linkage and drive
The Power Seat Module

Look underneath with light and mirrors. Or remove the seat to look.

Help in the link

https://www.google.com/search?q=mercedes+cl550+seat+lift+not+working

..

Check the chain-drive located under the seat. (but watch your fingers)

It may be the switch is failing and needs to be replaced. However, it is not unusual for the motor moving the seat forward and back to jam on the running teeth attached to the seat. If, when you use the switch, you can either feel or hear the motor trying to run, then it is probably a mechanical problem under the seat. This can have a few causes - something on the teeth that should not be there, alignment of the motor to the teeth (maybe loose bolts), etc. If this is the case, the only way to troubleshoot this is to remove the bolts holding the seat frame to the floor, then using the motor move the seat as far back as it will go, then tip the seat forward and inspect the motor and gears underneath.

if going backward is working,and foward is not,, easy
,1st determine what is defective-so u know what to replace/repair-2 things only ,[1-switch or 2- motor under d seat]
by presing the backward swicth,, you can hear the sound of the motor running and u can see the seat is going backward...
1-now by pressing the foward switch, and you hear the motor running but not that strong like the rear ..and the seat move an inche /a little and stop,,.then u have a defect weak motor,
2- now by pressing the foward swicth and u dont hear any motor running then the switch is most likely defective
defective switch -repair- spray contact cleaner,remove cover switch,penetrate inside
defective motor-repair-remove motor replace inside carbon,,.chiepest way not to spend to much money..
i suggest even once a month,lubricate all power seat/even not powerseat/,door hinges/.trunk door/.power antenna./ .by spraying lubricating oil,. for maintanace,..you can save a lot..

I would say the cables or rods that go from the motor to the gears are broke or stripped.

YOU HAVE A SWITCH OR A TILT ACTUATOR MOTOR PROBLEM. LINCOLNS HAVE 5 OR 6 ELECTRIC MOTORS MOUNTED ON THE UNDERSIDE OF EACH FRONT SEAT WHICH REQUIRES REMOVING THE SEAT TO INSPECT .THEIR ARE ALSO CABLES ATTATCHED TO THESE MOTORS SO LISTEN WHEN YOU HIT THE TILT SWITCH DO YOU HEAR A MOTOR NOISE? IF YOU DO THEN YOU MAY HAVE A BAD CABLE.

check for something jamming the track under seat , try havin son push seat forward while pushin switch . i dont know of a way to override the seat motor if its dead,,auto wreckers for seat replacement cheapest way to go they may even install

So here is a diagram of the seat circuitry for your car. Since every other function works except the forward/backward slide function, that leaves basically the forward/backward slide motor, the seat switch, and/or the wiring. If you can verify that the wiring under the seat is in good condition without obstructions, chaffed wires, and/or wires pulled too tight, then it's safe to say it's down to just the motor and/or the switch. Sometimes if the passengers front seat has the same switch, you can plug it in to the drivers' side connector and see what works and what doesn't. If the seat works fine with the other switch, then that's all it needs, if not then it will need a motor. If the other seat doesn't have a switch then you can find them at wrecking yards, or just supply power and ground to the motor in question to see if it works. If it does, then you know you kneed a switch and if not then a motor.
I hope this info helps!~subyguru~

can you hear the motor trying to run?

It has a separate motor for each function. Could be binding on the track too. try pushing forward while hitting hte switch

I'm assuming this is a power seat. If so, there are separate motors that control the various functions of the seat such as forward/backard, recline, lumbar support, etc. It could be that the motor or an electrical connection to the motor for the forward/backward motion is faulty. Normally all of the motors would be on the same power circuit, so if some of the functions are working then it is probably not a blown fuse.

Just one other personal observation, I have actually seen an instance where some loose pocket change had spilled under the seat and a quarter had become wedged in the track that the seat slides in and had jammed the tracks so tightly that the seat would not move.

One thing to note is whether or not you hear anything when you try to move the seat forward/backward. If you hear a click or a buzz when you press the button then that could mean that something is physically jamming the seat tracks. If you don't hear anything when you press the button, then that more than likely means a problem with the motor or the electrical connection to the motor.