Unfortunately, that is the soft-close actuator, not the lock actuator. The soft-close actuator is accessible on the bottom of the actuator assembly, while the lock actuator is buried deep inside the assembly.

I had the same problem, and couldn't see any way to replace the diaphragm that is the probable cause.

That being said - try resetting the computer first. You didn't tell us what car you have, but on the 2003 S430, you pop out the floor light housing located behind the right rear seat passenger's heels, then remove and replace the 20-Amp fuse. This will cause the computer to try the faulty lock for a few times. If that doesn't help, you probably will have to replace the door actuator assembly. I paid $465 delivered from oediscountparts.com

It isn't something you want to do twice...

 

the soft close on that door also doesn't work. And if it's quiet, I hear an air sound in that door after the others have locked. If I didn't have soft close functionality, that would be ok. But I need to get the lock to work because using that little metal key blade isn't working for me.

 

Just had the same thing happen last month and successfully made a 'bubba' repair. Its been working for a month, not sure how long it will last.

The actuator vacuum and pressure components are connected via the PSE pump and soleniods between the two actuators. Not exactly sure how it works, but here is what I did for a repair.

Remove the door panel. Remove the outside door handle. Pull out the actuator. There are other threads on how to accomplish this.

When I opened the door panel, the white actuator cap was broken off. The lower snap ring had broken off. To make a repair, I reinstalled the white cap, wrapped black electrical tape around the broken base for (somewhat of) and airtight seal, and zip tied the white cap back to the actuator. See photos below.

Not sure how long it will last, and the $100 new cap is not a bad gamble for repair. I would not consider a used actuator, because the plastic embrittlement will eventually take out the most used white cap (driver's door) even if the used is not yet failed. A $600-$800 new actuator is ridiculous IMHO.

 

Some other items of note. Softclose worked prior to the repair on the driver's door, but now it does not. Seems I have traded softclose for door lock actuation and not sure why. The other door locks now work more smartly, they took much longer when the DD lock actuator was failed. I will go after this in the future.

Reinstalling the outside door handle has a blind fit with an actuating rod that is secured using a simple friction fit and white plastic snap. It will come undone with slight force when removing the actuator, so it is good to get a feel for its arraingement while the actuator is still in the door panel. (Pointing to this clasp on the back of the actuator in the photo)

You will have to drill out rivets for the window actuator to remove the door actuator. You will need a mild magnet on a stick to get out the rivet backings or risk rattles in the bottom of your door shell. (Not enough room for a vacuum) I did not rivet these three connections back in during reinstallation, but instead used large head stainless steel short length bolts (M8) and locktite.

Check your work during each step of reassembly (e.g. lock-unlock). I used this approach, and still had to backtrack once when I knocked off an airline. I also did not detect the softclose problem until finished.

Cost: 2.5 hrs, 6 inches electrical tape, 3 bolts/washers, locktite and 4 zip ties.

 

Skyland Automotive furnished a driver's door actuator for $465, including shipping. This was a Mercedes part from a Mercedes dealer thru their online sales department. Good people to deal with - they will answer tech questions on the phone for their customers. If you prefer phone orders, their number is (828) 667-5213 - ask for Greg. No affiliation, except as a satisfied customer.

 

I didn't get the door lock actuator out because I didn't drill the rivets on the window regulator and take the window regulator out. I unbolted the lock actuator but I guess you can't get it out of the door without removing the window regulator.

I then noticed that the black hose was not attached to the white bottom cap. I plugged the black hose back into the bottom white cap and it started working. I circled the part on a picture I found on the internet. Maybe this will help someone.

 

Good show! Looks like you fixed your door lock problem with the lowest cost and effort.

 

I realize this is an old thread but I have the same problem with my driver's side door. Happened a couple of weeks ago. 2003 S500. I just haven't had time to thoroughly check it out.

I'm considering going for that plastic piece on the bottom to see if that fixes the problem. All of the other doors worked (before I pulled the 20amp fuse out to keep from burning out the PSE pump). I believe the plastic piece is the culprit because I heard this cracking noise inside the door when it tried to close (sounded like someone squeezing one of those plastic water bottles) and a hissing sound coming from the vacuum line.

Since you have been through this operation already is it possible to replace that white cap without taking the actuator out of the car and dealing with all of the cables and door lock mechanisms? I don't want to have to drill out rivets unless it is absolutely necessary.

One other question should the window be rolled up or down or mid-way during this process. I have read just about everything I can find on this subject and there are several mentions of removing the window guide rail to get the actuator out but no one mentions what position the window should be in.

Any help would be much appreciated.

 

I had no crunching sound, just an air leak due to a disconnected air hose. So, I don't know what yours is.

Anyway, I could be wrong but I imagine you'd have a pretty tricky time replacing that plastic part without removing the door lock actuator first.

I don't remember exactly, but it might or might not be possible to get the entire assembly unbolted and get the bottom to stick out of the opening to do that repair. But maybe not If you try that and can or can't do it, let us know.

As far as removing the window regulator track, that might have been one of the things or the thing in the way of getting the lock actuator removed. Maybe the rivets would have to be drilled out on that to get it removed.

 

Not clear whether your problem is lock/unlock or soft close. The plastic actuator visible on the bottom of the door locking assembly is for SOFT CLOSE. It can be fixed. There are several videos on You Tube for this repair.

The DOOR LOCK/UNLOCK actuator is buried deep in the door locking assembly, and I couldn't see any way to get to it for repair. I had to replace the entire assembly. There is a very small possibility that you might have a broken air line or something else that could be fixed, but my impression is that the actuator is the more common failure.

 

I'm almost certain it is the white plastic cap at the end of the actuator. Yes I do have soft/close. The reason I am thinking it is the plastic piece is because all of the other doors soft close work as they should. I'll pull the covers off sometime this weekend and see what's going on in there. Getting the door panel off is the easy part. After that is when the fun starts to happen.

From everything I have read and all of the pictures I have seen this thing can be a beast. I'm sure some of those rivets will have to be drilled out (car was assembled by robots). I'm sure the MB folks use rivets so that the part doesn't come loose.

Either way, I'll put updates on the mbworld and this forum.

 

Window stayed up during my 'bubba' repair - which is still working a year later.

I still don't have soft close on the driver's door, but all I really needed was remote and auto locking capability.

IMHO - Don't see how you can accomplish much without removing the regulator.

 

The guys that had the problem already and have taken care of it, to fix the soft/close, does the actuator need to come out or it could be done without removing it ?? I am on the same boat with few of my doors soft/close gone bad and the only way I will tackle it will be if I don't actually have to drill the actuator out. Please if any one can chime in....Thanks in advance.