When mine acted that way it was the "motor module" (CAN). It seems that was a common problem. I got another out of a wrecking yard and so far so good.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Replace or clean and reinstall your fuses. Might just be some corrosion.

Thanks for everyones replies so far. mpolli, what exactly is the CAN, and where is it located?

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2006 E320CDI- current dd
1999 E300TD - retired
Wilmington, NC USA

The CAN bus is a serial data bus that controls accessories on new cars. That way they don't have to run power wires from every switch. On the motors there is a CAN transceiver module that receives the commands to go up or down. It is integral with the motor. So essentially you would change the motor. However, I don't think anyone sells just the motor. They do however sell just the cable/track mechanism so if you are buying aftermarket be careful what you are getting. I cannot guarantee that is your problem but the symptom is the same as I had and I think MB Doc would tell you the same thing. Maybe he will chime in on this matter.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Actually I guess I got lucky. The link off this website to allpartsexpress.com has the genuine MB window motor for the left side for $137.00, which is the side thats broken. For some reason its about $50.00 cheaper than the right side.

I have changed out entire window regulators before on domestic vehicles but never on the MB. Is it difficult? Is removing the door panel tricky? Thanks.

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2006 E320CDI- current dd
1999 E300TD - retired
Wilmington, NC USA

That is lucky! I would think they would be the same motor as my car but I guess not. Anyway, I think you can find quite a bit of info on this by searching but basically this is how it goes:

First remove the door panel. This can be a little tricky the first time so search for the instructions for that car.

Once you have the door panel off you have to peel off the plastic liner to have access to the window regulator. You must drill out the rivets that secure the window regulator to the door. I used a 1/4" drill to drill the head off, then punched the rest through with a center punch. Then remove the plastic clip at the bottom of the window. As I recall there was a white piece of plastic (the "clip") that I pulled down (or up?) and then then there was a plastic "cam" on the bottom of the window that slid out of a "channel" on the regulator. I did all this with the window up which seemed to be best, and I put a piece of tape on the glass to hold the glass up while the regulator was out. The motor is held on with 3 big Torx screws and comes off easy. Put the regulator back in and attach to window before riveting of course. New rivets are pretty cheap and you should have ordered those at the same time you ordered the regulator, otherwise you can get them at the dealer for about 1.50 each. You need an extra big rivet gun and a strong grip! When you are all done be sure to reseal the plastic film so it is waterproof. Ask me how I know this... Good luck

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra