Recently, my driver side window has been making a loud 'clunk' as it hits the end of its upward travel, as opposed to the softer stop that the other 3 windows have. It goes down nicely though.
Does anyone know how this is supposed to work? In other words, I think something shuts off the motor just before the window glass reaches the physical limit of its upward movement, so it won't 'bang' when closing, so if I knew what does this, I'd know what to fix. (and if the job is worth doing, as it does mean door panel removal first).

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1986 560SL
2002 Toyota Camry
1993 Lexus

It probably means your regulator is going bad. If you take off the door panel you may be able to see that one or more teeth on the regulator are missing or ground down. The solution is a new regulator which is maybe $100 and a couple of hours of DIY labor, although it can be a frustrating couple of hours.

One of the screws holding the regulator to the door sheet metal serves as an "adjustment." When you install a regulator/motor assembly, using this screw you can adjust between won't work and works smoothly. I'd propose "out of adjustment" is more likely than "broken tooth."

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

Sounds like all the bolts on the regulator are loose.

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Auto Zentral Ltd.

Thanks to all for the input. When the rain lets up I'll buckle down and take off the panel to find out which theory is right, and post back results.

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1986 560SL
2002 Toyota Camry
1993 Lexus

donbryce,
Thanks for the thanks, and if you post your findings, you will be among the few that do. My hat's off.

Good luck,

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Auto Zentral Ltd.

Mine did the same thing just before this part broke:
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1MB12FET61N91D13MR&year=1987&make=MB&model=300-SDL-001&category=O&part=Window+Regulator+Kit

Pretty simple fix.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

My 300SE had that prob and it turned out to be both the window regulator teeth and the sheet metal onto which the regulator bolts onto was bending. The sheet metal fatigue seems to be common on the Se's.

Same car's rear driver side window would not lower with motor, That turned out to be just the plastic bushing referred to by the previous poster.
Anyway, symptoms have diff incarnations.
Take the panel off and snoop.

Den

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1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
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1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

My sheetmetal actually cracked. JB weld and a piece of scrap metal to the rescue. Stiffening the sheet metal was enough to stop the gear teeth from jumping although it was worn quite a bit.

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82 300D....went to MB heaven
90 350 SDL....excercising con rods