[R129 SL] r129 sticky window

[Rob Vonderhaar]

Here's a link to step-by-step instructions for removing an R129 door panel (even includes color photos!).  I've used these myself and they're perfect:  http://www.astro-nut.com/mb-door.html

Can't give you much advice about the mechanism without first getting the door panel off and taking a look.  You'll probably find a problem with either the motor or regulator.  I had similar trouble with my '95 where I first started getting a loud metallic "clank" sound when the driver-side window reached the full-down position.  The problem continued to get worse until the window jammed about halfway down and wouldn't move in either direction.

After pulling the door panel, the problem turned out to be the window motor itself, which mounts to the inside of the door frame with three bolts (the regulator is actually riveted to the door frame).  The OEM Bosch motor had a black molded plastic body - the bolts pass through the holes in the door frame, then through some metal standoffs/spacers about ½" long, and finally into plastic 'posts' in the motor body.  An incredibly stupid design, because there's huge torque on those three motor mounts as the tiny motor gear drives the window regulator up and down.  Eventually, the plastic posts into which the mounting bolts fit cracked into pieces (I found several at the bottom of the door cavity), and this lets the motor flex or even move when torque is applied.  The 'clank' sound turned out to be the motor gear jumping its teeth against the regulator, which also destroyed the gear teeth over time.  Only fix was to replace the whole motor assembly.

If you do find yours broken this way, shop around:  I located a used motor on eBay from a 1992 SL at about half the cost, but more importantly, it turned out to be made by a different OEM in the earlier cars and had a nice cast metal body instead of the cheap plastic used on the newer cars (plastic is also used on new replacement motors).  The metal body also didn't require the use of spacers, so the whole assembly is much stronger and more stable.  While I had everything apart, I also re-greased the regulator gear and the vertical tracks until I could manually pull the glass up and down smoothly and with little effort.  It works like new, and no more problems since then.

Hope this helps!
     Rob Vonderhaar
     Leesburg, VA

PS - If you haven't done it yet, you might want to think about replacing the door strap at the same time.  It's a $25 part that frequently breaks on the older cars, and takes only minutes to replace while you've got the door torn apart.  Otherwise, you'll have the fun of ripping it all apart again later like I did...  :)

From: r129list-bounces at mbcoupes.com [mailto:r129list-bounces at mbcoupes.com] On Behalf Of gerhard stefandl
Sent: Saturday, December 13, 2008 4:06 PM
To: r129list at mbcoupes.com
Subject: [R129 SL] r129 sticky window

I have a '94  sl500 and suddenly the window jams when I lower it. I'm figuring that the drive mechanism is worn, but I can't get the door panel off , and am afraid to yank on it too much, for fear of cracking it. Can anyone advise how this is done. Also, does anyone have advise about the window mechanism.

Thanks for the help.
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