This DIY was made during the replacement of the ignition switch in our 1996 E300D. It may also apply to the other 1996 and 1997 W210 cars. Parts of the procedure, specifically the removal of the driver's under-dash panel, may apply to the 1998-99 W210 cars. These later cars have a different form of ignition switch that is much harder for the individual to R&R due to the fact that they are electronic modules that must be programmed for the car into which they are being installed.
This is a rather long DIY owing to my love of reading my own writing. For those who lack the patience to tolerate my verbosity, just look at the pictures.
Removing the driver's under-dash panel. This operation is necessary to R&R the ignition switch as well as the many other goodies that hide under the dash on the driver's side.
Before I began this job, I searched this and other forums and asked for pictures and instructions. Several people were kind enough to share their cache of information with me. Although I learned quite a bit by reviewing these contributions, it soon became clear that much of the information was (at least) misleading or (worse) wrong. As I figured out what was really the correct procedure for my car, I took the notes and pictures that resulted in this DIY.
To make as much room for yourself as possible, put the driver's seat as far back as it will go and extend the steering column all the way out and up. You can disconnect the battery at this point although it is not really necessary (do you know about the plastic panel, behind which is a negative cable connection, so you don't have to remove the rear seat?).
The first picture shows the six fasteners that must be removed before the driver's under-dash panel will come out. The panel is reinforced with sharp-edged sheet metal. Later pictures will show what happens if you do not get all the fasteners out.
Fasteners #1 and #5 are simply screws. Fastener #3 is a plastic nut. Use a pry tool and a screwdriver as shown in the next photo to remove it.
Fastener #4 holds the under-dash heat vent. Turn it 90 degrees counter-clockwise and remove the vent by pulling it out at one end as the pictures show.
Fastener #2 holds the hood release and is hard to see -- it should have been designed to be on the other side of the lever. With the screw out, the hood release will pull down out of the panel. Using two hands, operate the lever to pop the hood open and leave the lever bent, so that you can remove the cable from the plastic parts. You will see how to do it once you get the lever into your hands. The cable can be left dangling through the hole in the panel. Don't try to remove the OBD-II connector at this time -- we'll get it after the panel comes loose.
Fastener #6 requires an 8mm socket on a fairly long extension. It is hidden up inside the panel and must be removed before the panel will come off. You must operate by feel. A magnetic socket would be nice.
The panel is reinforced with sharp-edged sheet metal. My failure to discover fastener #6 lead me to pull down hard on the front edges of the panel, trying to get it to come free. This resulted in two badly-cut finger tips. The pictures shows my left hand after several days of healing. Learn from my mistake, people!
With all of the fasteners out, removal of the panel is now simply a job of releasing all of the hidden clips, hooks, and hangers along the edges. The next four pictures show all of them.
Now the panel will drop down so you can get at the OBD-II connector. Leaving the plastic frame screwed to the panel, push the release clip shown in the next picture to the right (red arrow). Comment: I use a Red Arrow to honor my Canadian friends. This will release the cable and the connector, which will pop out of the frame. Leave the frame in the panel and the cable dangling (along with the hood release cable) and carefully remove the panel from the car. You are now ready to operate under the dash.
To re-install, simply reverse the removal procedure. Put the panel back in the footwell and replace the OBD-II cable, then thread the hood release cable through its hole. If you are concerned about it getting loose and going up through the hole, just put the lever back on the cable so it blocks any attempt of the cable to escape. It will take some wiggling to get all of the hooks and snaps that hold the panel to the frame of the dash to connect. Work gently and patiently until the panel is back in place, smacking the reluctant places with a fist (especially the plastic hooks under the steering column).
Here is the second part of the procedure, which I never posted as promised in Part 1 (sorry!). This applies to 1996 USA models only. It might apply to other parts of the world, I don't know. It does not apply to the 1997 E300D as that model got the $500 electronic switch, more's the pity.
Disconnect the battery negative cable as a safety precaution.
To unscrew the ignition switch bezel, you need a special US$50 Mercedes tool, 639 589 01 07. You may be able to use a pair of needle-nose pliers, just don't booger up the dash covering and then blame me!
The key must be in position 1 and must never, never, never be moved until the whole thing is back together. If you violate this rule, the ignition switch locks internally and cannot be fixed or so Mercedes says. I would tend to believe that.
If you use a bare key without your entire household key ring hanging from it, the lock will be much easier to remove. (The key must stay in the lock as it is removed from the dash.)
Remove the cable from the ignition switch assembly.
With the cable out of the way, use two small screwdrivers or pin punches to depress the two spring-loaded pins that hold the switch assembly on the steering lock. The steering lock stays in the car.
With the pins pushed in, the ignition switch module can be pushed forward (towards the front of the car) and come out of the steering lock. Now you can unscrew the transmission lock cable.
The assembly consists of the ignition switch and a plastic "sleeve."
Follow the instructions in the next picture to remove the switch from the sleeve. The sleeve doesn't have to be replaced and is also expensive so you don't want to break it in the process. The lock stays in the sleeve and the key stays in the lock. Make sure you take pictures so you can put the new switch back exactly as the old one came out including being in position #1
I never got an explanation from the dealer as to the change in part numbers for the ignition switch for my '96 E300D. I brought the old switch with me when I went to the dealer. They ended up finding the replacement switch listed for another car, I don't remember which, possibly an S-class. For my car they found in EPC the 1997 electronic switch which is (a) wrong for my car and (b) US$500.
You have to move a plastic piece from the old switch to the new one.
I discovered after buying the new switch that the old one simply had burned contacts and was repairable. I took the switch apart and buffed the brass (copper alloy?) contacts. The repaired old switch now lives in my spare parts box.
Put the new/repaired switch in the sleeve and make sure it locks in place. Reattach the transmission lock cable. Put the assembly back into the steering lock. The upper pin may be hard to get depressed. Both pins must pop back into place. Make sure they do. Put the electrical cable back on the switch. Screw the bezel back on. Before putting the lower dash cover back, try the switch (mechanically) to make sure it works properly. Then reconnect battery negative and try it electrically.
I think that's it. Anyone spotting errors please advise so I can edit. No warranty is expressed or implied. YMMV.
Discuss this DIY here.