300Se W126 illustrated window regulator jaw fix - PeachParts Mercedes-Benz Forum

unkl300d · #1 11-28-2009, 03:40 PM

My 1989 300SE had a broken passenger rear side window regulator jaw break.

I had the other side's jaw replaced many years ago by a mechanic so I did not know how to do it myself until I read the archives of this forum and gathered some ideas for this time around.

Remove the associated hardware that hold the door panel. Don't forget the 'wing' molding at the top side of the window and the door lock.
The door panel pushes upward to get it off.
I included a picture of the panel backside so you can see that it has plastic hooks and therefore should not be pried off. You will bust it up otherwise.

Peel back the plastic humidity guard. It is reusable and should be taped back or glued back on afterward.

You will need to reconnect the arm rest and attached window button in order to complete the circuit and be able to use the button for window regulator operations.

No need to remove the regulator or motor.

The glass can be manipulated by hand in order to get it out of the way.
It holds in place on its side runners or you can wedge something to keep it set wherever you want it.
I left the regulator arm in a down position in order to have access to it.
I pulled the glass upward and out of the way.
Place some wood shims behind the arm in order to give a resistive backing.

The original OEM rivet that holds the white plastic jaw has a slight mushroomed mound on the outside arm face.
This can be ground down using a cordless drill and a basic grinding point.
I preferred the fine edged one. It grinds down with ease so don't over do it and cut down the arm surface.
As you grind down the body of the 'mound', look clcosely and you will see the outline of the rivet shaft appear.
Grind down flush to the arm's surface.
Get a curved jawed vice grip and grip the inner facing rivet's round end and begin to rotate it. You will see that it can be rotated easily. Observe for edges of outer rivet spurs that may need extra grinding in order to free the rivet.

With the large or even a small vice grip you can work the rivet off without having to drill it out. Use another vice grip to hold the regulator arm while you work the rivet off. You don't want to bend or warp the arm.
Use common sense. Take your time.

Once the rivet is off there is no need to clean off the innner facing surface of the arm.
The exposed hole is about the same size for a 1/4" by 3/4" stainless steel clevis pin. I only had to ream the arm hole it a bit with a 1/4" drill bit in order to fit the clevis pin through. Don't over ream because a snug fit is what you want.

Now you have to take apart the new plastic jaw. Use a small flat head screw driver to draw back the plastic clips. Push from outside toward inside-center with the jaw's protruding surface facing you. One side snaps off easy. The other side gets hung up a bit by the installed pin. So with care finesse that side off and the backing of the jaw comes off. Don't lose the black plastic 'bumpers' and the thin 'wafer' washer.
Install your clevis pin and use the thin washer and one new metal washer to keep the new clevis pin from slipping forward and out of the jaw body.
The jaw is now ready to press and snap together by hand. Easy does it.
Don't be alarmed that the back of the clevis pin can drop out of the jaw's back side round hole. When you install the jaw into the galss track, the track's back side holds the clevis butt in place.
You may not feel that you need the following but I installed it. The clevis pin's girth is slightly smaller in diamter that the original pin's body. So I bought a steel spacer 1/4 " by 3/8" by 1/2".
I placed the spacer on a flat jawed vice grip and used a hack saw to cut an appropriate length collar.
Notice that the new jaw's original pin slightly extends past the protruding nose. That approx 1/16" length is what I cut. File down the cut sside to flatten out the cut. The collar fits right down the clevis shaft and into the jaw's nose. It makes up for any internal slack.
The picture shows the bagged whole steel spacer and outside it the remains of the cut item (not the installed collar).
The pink circle encloses the removed new jaw pin and the blue circle encloses the old removed pin.
A sample of the new replacement jaw assembly is in the picture. I bought two in case of problems.
I had also purchased some alternative clevis pins and screw posts (steel NOT aluminum) in order to have handy option and alternatives. The clevis I used worked great so I did not fall back on the options.

Put the newly assembled jaw in the glass track. Manipulate the glass and track until it matches the regulator arm and receiving hole.

I used two metal washers with the old jaw's thin wafer washer over the clevis and arm before putting in the 1/16" by 1 " steel zinc plated cotter pin.
See the picture of the assembled arm/jaw.

The clevis pin and cotter pin I used are not shown seapartely in the parts picture.

Put some new grease on the tracks ( I used garage door white grease) and put it back together carefully.

Don't rush the process and it ought to go well. Home depot had most of the pins etc. I bought from other hardware stores also.

Thanks to the other members who posted threads with clevis pin pictures !

Replace the door panel with care. Its not that easy to align the hooks and set it flat. Especially the ones down in back of the ash tray bin area.