Great Web page...
I saw a similar posting but different model and different symptoms. I have an '89 300E and the drivers side window ceased working. It failed a couple times previously and started working again. Been dead now for a couple of weeks. Where do I start??

I'd check the switch first.

Pull out the carpet under the armrest and remove the single screw. Remove the plastic rim around the gear shifter and pull up the wood panel. The window switches can by removed just by pulling them out. You can swap right/left switches to see if that's the problem.

The switch is very likely to be the problem, IMHO. You'll probably find all kinds of gunk down there (crumbs, spills, etc.) that could cause it to fail. In my 90 300E I just opened up the bad switch, cleaned the contacts with fine sandpaper, and reinstalled.

Hope that helps.

Thanks for the quick reply and I am very happy to hear that the switch is likely the problem. I was all set to check the switch this weekend and could not get the carpet out without feeling like I was going to damage it. Are there any tricks?? Is it just tucked in or glued or what???

On my '91 300E the carpet would lift up in the front enough to access the screw. I didn't notice any glue or adhesive.

Use a credit card to pry up the plastic ring around the shifter. Be sure to take note of the orientation so you reinstall it the same way it came off.

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'98 E430
MBCA-Peachtree

The switch is good.....
I swapped it with the right side and right side still worked and left still didn't. Switch connector seems fine...actually quite clean in there. Any other suggestions for a weekend mechanic or am I rapidly approaching a trip to the dealer.??

Does it make any difference if the door is open or closed? You might move the door while pressing the window switch just to see if the wire harness running into the door near the hinges has broken but still makes intermittent contact.

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'98 E430
MBCA-Peachtree

Is the fuse in order??

If both of the rear windows work fine, then you probably have a problem in the window motor.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

I ran into this problem in both my 87300 E and my 88 Acura Legend. My local body shop indicated that after a winter of leaving the windows up, sometimes the rubber molding around the window will adhere to the glass tightly enough that the window motor can't develop enough power to sheer the window loose and allow it to lower. In each car they ran a thin section of plastic between the window and the molding, which allowed the window to lower. They applied a "rubber protecting liquid" around the molding, and closed the window. I have not had a problem with either car since this was done. Hope this helps.

I just took the door apart and have confirmed power to the motor. It's not clear to me how the motor is removed. Does the regulator need to be removed to work on the motor?? Is this something a fair to middlin' weekend mechanic can do or should I plan on going to the dealer??