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Front Door Latch and Vacuum Solenoid Replacement on your Mercedes Benz
 
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Pelican Technical Article:

Front Door Latch and Vacuum Solenoid Replacement on your Mercedes Benz

Steve Vernon

Time:

2 hours2 hrs

Tab:

$80 to $600

Talent:

***

Tools:

Phillips screwdriver, trim removal tool, 8mm, 10mm socket

Applicable Models:

Mercedes-Benz W201 (1984-93)

Parts Required:

Latch and Vacuum Element

Hot Tip:

Door panels are expensive, take your time

Performance Gain:

Not getting lock out

Complementary Modification:

Replace window regulators.

This article will show you how to replace your front door latch mechanism and vacuum element. To get to these you will need to remove the door panel, and while it is not a difficult job, the door panels can be very expensive so take your time and double check things

Before you begin you should park the car on as level ground as possible. Nothing is more frustrating that trying to work on the door while it is swinging open or closed. It is also a good idea to get yourself a small box or container to keep all your parts in.

Begin by rolling the window all the way up into the fully closed position and remove the key from the ignition. Next, remove the plastic lock along the upper ledge. It just unscrews counter clockwise. The door panel is only held on by two (2) attached pieces of hardware. The first is the door latch/lock trim piece. Remove this piece by unscrewing the Phillips screw and pulling the trim piece straight back.

Second is the door pull handle. Begin by removing the set of control switches for the power seat. Using your trim removal tool, gently pry off each piece. The seat switch rides on a small cylindrical post that has a circlip attached to it. Remove this clip using your needle-nose pliers. Once the clip is off you can use you trim tool to remove the cover plate for the seat switches. Unscrew the screws holding the switches to the door and pull them out from the door.

Next using your trim removal tool, remove the trim piece at the top of the pull handle. Underneath, remove the 10mm nut. Now you can slide the housing for the interior door handle forward and out of the panel. Once it is forward, you can remove the actuator rod that connects the handle to the lock assembly behind it.

You have now removed everything that is bolted to the door panel. The Mercedes-Benz door panels are different from most other manufacturers in that they do not use compressible clips to hold the panel to the door. Mercedes-Benz panels are held on by hard plastic hooks that sit within pockets in the sheet metal of the inner door. Once you have all the hardware off the door, you simple need to lift the panel up and away from the door.

If your car has door mounted speakers disconnect the wire running to the speakers where it joins the unit, then you will need to remove the four 8mm nuts holding the unit on. With the speakers removed you will have access to what is referred to as a "vapor barrier" between the panel and the door. It is really just a piece of plastic held on by glue, and is used to keep out any wind, weather or noise from the door getting into the interior of the car. If you are going to be doing further work on your door, carefully, and I mean carefully, try and remove it in one piece so you can reuse it when putting the door back together. If you damage it, you can get some thin plastic sheeting from your hardware store and recover the door with it.

To remove the latch you will need to first remove the exterior door lock. Begin by opening the door and using your trim tool to remove the grommets along the inside section. Once the grommets are removed, you will see a small 3mm Hex screw. Loosen but do not fully remove this screw (this job does not require complete removal of this screw). If you do, there is a very good chance it will fall into the door cavity.

Once the Hex screw is loose, insert the key into the lock tumbler. Turn the key approximately 60° degrees clockwise while simultaneously pushing the mechanism towards the rear of the door. This will free up the lock and allow you to remove it from the door.

You want to remove the latch, vacuum element and pull lock as one unit. You can replace the element by itself but it is very difficult to disconnect and reconnect it to the lock actuator and pull while it is in the door.

Begin by removing the three large Phillip heads screws that hold the latch to the door. Two are on the closing edge of the door and one is on the inside. The two that are on the closing edge are secured with a surprising amount of force. They can be very difficult to remove and strip easily. I had to use an impact screwdriver to remove the ones on our project car. An impact screwdriver is a tool that you can insert different screw bits on one end and strike with a hammer at the other. The driver delivers a strong and sudden force to the head of the screw while pushing the bit into the head. Pelican Parts sells a complete line of impact screwdrivers. If you start stripping the head of one of these screws, stop, and get yourself an impact screwdriver.

Reach into the door frame and unplug the wire going into vacuum element. There is a yellow vacuum line going into the bottom of the unit but it is easier to remove once the unit is free of the door.

Unscrew the two 8mm bolts holding the element to the door frame..

With everything unscrewed, reach in and lower the latch and element towards the bottom of the door, taking care as the pull lock clears the frame. You can now see where the yellow vacuum line is connected to the element. Disconnect it and set the yellow aside in the door. You will need to tug fairly hard to get them to separate, so make sure you grab the vacuum line by its connector and not by the line, as the line may break if you pull too hard on it.

Now that everything is disconnected and bellow the cross member in the door, carefully turn the unit towards the inside of the door to clear the window regulator rail. The unit should pass between the regulator rail and the outer door skin. Remove the complete unit from the lower access hole in the door.

Take the latch and element to your work bench or lay them on a flat surface. There is a small plastic bushing that connects the pull lock, vacuum element and door lock/latch together. If you are replacing the latch mechanism, gently squeeze the bushing together on the open end and slip the pull lock and element from the door lock/latch. Put a small amount of lubricant on the new latch arm and reattach. If you are replacing the element, mark the element arm where it attaches to the plastic unit. Unscrew the old unit and screw the new unit onto the arm, setting it at approximately the same height or mark as the old one.

Installation is the reverse of removal.

Shown here is the interior door panel.
Figure 1

Shown here is the interior door panel. You will need to remove the door lock pull (green arrow) lock trim piece (blue arrow), and the trim pieces by the door pull and seat switches (red arrows).

Begin by unscrewing the door lock pull.
Figure 2

Begin by unscrewing the door lock pull. It unscrews counter clockwise.

Next remove the lock trim piece by unscrewing the Phillips screw and pulling the trim piece straight back.
Figure 3

Next remove the lock trim piece by unscrewing the Phillips screw and pulling the trim piece straight back.

Using your trim tool remove the plastic pieces for the seat controls.
Figure 4

Using your trim tool remove the plastic pieces for the seat controls.

You will need to remove this small circlip (red arrow) before you can remove the trim face.
Figure 5

You will need to remove this small circlip (red arrow) before you can remove the trim face. Once the circlip is off, pull off the face plate, unscrew the two Phillips heads screws holding the switch unit to the door and remove it from the door.

Remove the door pull handle trim piece and unscrew the 10mm nut behind it.
Figure 6

Remove the door pull handle trim piece and unscrew the 10mm nut behind it. Once this is removed you can slide the complete handle piece forward and out of the door.

Once the handle unit has been pulled forward reach in and remove the actuator rod from the handle (red arrow).
Figure 7

Once the handle unit has been pulled forward reach in and remove the actuator rod from the handle (red arrow).

Lift the door panel up and away from the door.
Figure 8

Lift the door panel up and away from the door. Here is the interior of the door panel. You can see the 6 hooks that hold it to the door (green arrows). Insert upper right shows the plastic hooks.

Before you can remove the vapor shield (plastic along the door) you will need to remove the door speakers.
Figure 9

Before you can remove the vapor shield (plastic along the door) you will need to remove the door speakers. These are held in place by four 8mm nuts (red arrows).

With the speakers removed, you'll see the plastic moisture barrier on the door.
Figure 10

With the speakers removed, you'll see the plastic moisture barrier on the door. You'll want to carefully peel this off the inside of the door starting at the rear edge of the door. The idea is to peel it off in just a way so that it can be glued back onto the door later.

This is a picture of loosing the 3mm Hex screw that holds the locking cylinder in place.
Figure 11

This is a picture of loosing the 3mm Hex screw that holds the locking cylinder in place. All three of the door grommets have been removed in this picture. You will be using the upper, larger hole when you reassemble the door handle. You will need to reach in with either your finger or a screwdriver and make sure the opening lever on the door latch sits in the groove on the exterior door handle.

Insert the key into the lock and turn clockwise approx.
Figure 12

Insert the key into the lock and turn clockwise approx. 60° degrees. While doing this, slide the tumbler back towards the rear of the door.

Remove the tumbler by releasing the key and pulling it out of the door.
Figure 13

Remove the tumbler by releasing the key and pulling it out of the door.

Slide the handle towards the back of the door and then out.
Figure 14

Slide the handle towards the back of the door and then out.

Before you disconnect the element from the door, reach in and remove the electrical plug.
Figure 15

Before you disconnect the element from the door, reach in and remove the electrical plug. There is a yellow vacuum line attached, but it is easier to remove once the unit is free and lower in the door.

In this photo you can see all the fasteners you will need to remove to be able to pull the door lock/latch, vacuum element and pull lock from the door.
Figure 16

In this photo you can see all the fasteners you will need to remove to be able to pull the door lock/latch, vacuum element and pull lock from the door. Red arrows show the three screws holding the door latch. These can need a surprising amount of force to get them loose. We ended up using an impact screwdriver (insert lower left) to break them loose, as they started to strip trying to take them out with a regular screwdriver. If you strip them the only alternative is to drill them out! The yellow arrows show the two bolts that need to be removed for the vacuum element.

With everything free, lower the unit in the door frame until you can see the yellow vacuum line attached to the element.
Figure 17

With everything free, lower the unit in the door frame until you can see the yellow vacuum line attached to the element. Disconnect these. Make sure you grab the line by the stub and not the line. They can need a pretty good tug to get them apart, and if you pull on the yellow line you run the risk of ripping or breaking it. With the vacuum line free and the unit below the cross brace, turn the latch mechanism forward towards the inside of the door. The unit will pass between the window rail and the outer door skin. Remove the assembly from the lower access hole in the door.

This photo shows the complete assembly out of the car.
Figure 18

This photo shows the complete assembly out of the car. The upper pull mechanism (green arrow), the latch, pull and element joiner (red arrow) the door latch/lock (yellow arrow) and the vacuum element (blue arrow).

This Teflon bushing (yellow arrow) is a weak spot in the latch and can rip, weaken or just wear out.
Figure 19

This Teflon bushing (yellow arrow) is a weak spot in the latch and can rip, weaken or just wear out. Unfortunately at this time the bushing is not available as a separate part and if broken you need to replace the whole unit.

The yellow arrow shows the latch that connects to the outside door handle.
Figure 20

The yellow arrow shows the latch that connects to the outside door handle. When reinstalling you must make sure this is seated behind the door handle or your outside door handle will not work.

Here is a close up of the where the latch, element and pull join.
Figure 21

Here is a close up of the where the latch, element and pull join. If you are replacing the latch you will need to disconnect it from the pull and element. Gently squeeze the end of the plastic joiner and slip the pull rod and element from the latch. If you are replacing the element, mark the rod where it enters the element, then unscrew it from the old unit and re-screw it back into the new unit at approximately the same height. Installation is the reverse of removal.

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Comments and Suggestions:
rairden Comments: Driver door key-lock failure, turning the key won't lock or unlock. Followed steps in Fig 11, Fig 12, Fig 13 to pull the tumbler. Easy, no door panel removal necessary, but kind of finicky wiggling the assembly out. Found the broken connection piece, and compared it with a good piece on passenger side. Time now to visit a junkyard. Photo attached. No hurry, the trunk or passenger door still can lock and unlock everything.
November 18, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Jim Comments: When I try to lock the driver door that is, all of them with the immobiliser, the button goes down then rides straight up again. I can only lock up by pressing the button on the front passenger door. Any suggestions?
November 19, 2013
  Followup from the Pelican Staff: This sounds like a faulty latch. There may be a broken spring or corrosion stopping it from locking. - Nick at Pelican Parts  

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