Have 97 r129 the left window will go up but won't go down window down. Lowered the window with key trunk. changed the switch, when pressing the button up, goes up, pushing down, goes up. Any ideas? Thanks

Likely the module or regulator. The article I'm attaching is to get rid of power windows, but also talks about issues. Feel free to post a Comment just below the article and one of our techs will get back to you with more details.

Mercedes-Benz R129 Power Window Removal - SL500, SL320, SL600 (1990 - 2002) - Pelican Parts DIY Maintenance Article

I believe those had the CAN bus starting in 1996 (not sure). If so then a door module/motor is a likely culprit. Does it work from the central window switch? Do all the other windows work?

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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