HOW-TO: Replace your Ignition Switch

[RicardoD]

HOW-TO: Replace your Ignition Switch:
- on my 1994 E500 this is part number: 202-545-01-04-64

Step 1) Extend the steering wheel out to maximum extended position.

Step 2) Disconnect the battery negative lead in your trunk with a 13mm wrench

Step 3) Remove the lower dash cover under the steering wheel (using my photos from my turn signal switch How-to)

FSM link: http://www.w124-zone.com/downloads/MB CD/W124/w124CD2/Program/Chassis/68-150.pdf
- It was suggested to me to POP the hood first to make things easier
I will let the photos do the talking.






The lower dash will now drop and hang by the parking brake release lever, that is ok, no need to remove it from car.

Step 4) Remove the instrument cluster
- you will need two of the instrument cluster removal tools or you can make your own very carefully with a wire hanger


- you use two of these simple tools on the left and right side of the dash. Insert them carefully into the outer edge of the instrument panel, then twist to get the "hook" behind the instrument panel lip. You do this on both the left and right sides. Then with both left AND right sides hooks engaged you simple pull out the panel. It is a friction fit, it should pop right out.



Watch the first three minutes of this Youtube video if you want more info on how to use the instrument puller tools:

Step 5) Disconnect the large round instrument cluster connector on the left side. See the picture below which is AFTER I disconnected it. This will allow you to swing the instrument cluster out of the way of the working area you need to access.

 

[RicardoD]

HOW-To con'd

Step 6) Remove the two 13mm Hex head bolts that hold up the steering column. Once removed the steering wheel will hang down and you can move it around a bit.



Step 7) Remove the lockout cable with a 13mm wrench.


Step 8) With a 5mm allen tool tool remove this socket head cap screw underneath the steering lock assembly.


Step 9) Insert your key and turn to the Accessory 1 position. This will allow you to depress the Spring Pin which is all that is holding in the steering lock / ignition switch mechanism at this point.


Step 10) Depress the Spring pin with a small pointy tool (small phillips will do) and then move the steering wheel to the left (it is loose) and pull out the steering lock mechanism to the right.


Step 11) With some finagling (sp?), WHILE depressing that locking pin with a tool, you should be able to get the steering wheel lock / ignition switch mechanism free (some cursing is required here).

 

[RicardoD]

Step 12) A small celebration if you reach this point. Now you can easily disconnect the 3 connections to the steering wheel lock ignition switch mechanism including the large ignition switch connection on the back.





Step 13) holding the ignition switch so it is facing up (as the photo above shows), remove the three phillip head screws and replace with the new part. Everything is keyed so you can't put it together wrong.




Now reverse the steps to re-assemble!

 

[RicardoD]

Uncle Kent has some YouTube videos on the other bits in the steering lock. If you are doing a full restoration, I would consider replacing the entire assembly with new parts if you have it out of the car. And transfer over your keyed ignition tumbler. Uncle Kent warned about that blue cam mechanism inside and re-assembling it properly. I didn't touch it. You can put some lube inside while you have access. I can't say I understand everything fully but at least I got mine out and put it back in. And of course my HVAC fan blower works fine now.

 

[RicardoD]

I would also reference these notes from @emerydc8 , I can't say I totally understand how the steering wheel lock / ignition switch works.

Another Bad Blower Regulator? [Solved: Bad Ignition Switch] | Heating and Cooling (Interior HVAC systems)

This is the extraspecial M119 specific electrical diagram. I marked everything for easy reference. Assuming the PBU is spitting out the correct voltages, you could check fuse F15 or the PK/GN wires leading up to Fuse F15 or even perhaps that same PK/GN wire leading up the contact 15X in the...

www.500eboard.co

emerydc8 notes, must be from service manual:

There was a note that states that "the parking lock valve must be pushed back through the bore for the wire cable in order to remove the ignition key." I don't really know exactly what that means but all I did was screw the cable back onto the assembly only going hand-tight on the knurled thumb-nut. Everything seemed to check out okay so I tightened the jacket tube clamp with the Allen bolt, plugged in the electrical connections and closed it up.

I had same experience. When I finally had everything back together I was able to remove the key. But initially my key was locked in, I couldn't do the final twist to remove they key from the ignition switch. I re-installed the parking lock valve cable and then I got it to work but it is not as smooth as it used to be. I don't know if that is the new switch being "notch" or something else. I will update if it smooths out.

 

[emerydc8]

Excellent HOW-TO @RicardoD ! I didn’t think to remove the two 13 mm hex head bolts that held the steering column tight (step 6), so I didn’t have the room to initially remove the assembly as one piece as you did. I just twisted it on the shaft so it faced the floor and could get to the plug and three Phillips screws to swap out the switch. I wish I had thought to loosen the steering column then. There would have been less swearing!

Glad your a/c blower motor is getting the power it needs. Both my cars had blower motor power issues in the same year due to bad ignition switches and I think we as owners are going to start seeing more blower fans not working due to bad ignition switches (of course, this would be after replacing the blower and regulator—assuming they aren’t NLA!).

 

[nocfn]

Ricardo, thank you for the detailed write-up! Excellent as usual.

 

[Jlaa]

emerydc8 notes, must be from service manual:

I had same experience. When I finally had everything back together I was able to remove the key. But initially my key was locked in, I couldnt do the final twist to remove they key from the ignition switch. I re-installed the parking lock valve cable and then I got it to work but it is not as smooth as it used to be. I dont know if that is the new switch being notch or something else. I will update if it smooths out.

Thank you for posting this marvelous guide @RicardoD. I have a question about the step in red. My question is ---- what compelled you to try and twist and remove the key from the ignition switch (unsuccessfully) prior to re-installing the parking lock valve cable? Reassembly clearance concerns?

 

[gerryvz]

Add the ignition switch to the list of deferred maintenance for @Jlaa, which also includes the foam strips under and surrounding his headlamp buckets.

 

[Jlaa]

Add the ignition switch to the list of deferred maintenance for @Jlaa, which also includes the foam strips under and surrounding his headlamp buckets.

What @RicardoD didn’t tell you was that he ordered TWO ignition switches. One of those switches sitting at his house is mine. Along with spare parts to rebuild the 38 pin diagnostic connector.

 

[gerryvz]

What @RicardoD didn’t tell you was that he ordered TWO ignition switches. One of those switches sitting at his house is mine. Along with spare parts to rebuild the 38 pin diagnostic connector.

 

[Jlaa]

View attachment 163812
View attachment 163813
View attachment 163815

Heh. That foam stuff has negative ROI. You’re thinking @lowman, not me.

 

[RicardoD]

STOP THE PRESSES! (old man term)....

@nocfn reached out to me and pointed out a possible alternate method. But it needs to be confirmed @Jlaa. After you drop the lower dash you can try and disconnect the plug from the ignition switch leaving everything else in place. Then jam your head by the gas pedal and you may have access to the three screws holding the ignition switch in. Simply remove and replace the switch with the entire steering lock in position. This would really simplify things and exactly how I did the switch change in a my 1990 Porsche Carrera 4. Something for the next person to try *cough* @Jlaa *cough*.

 

[RicardoD]

I also have a question, every time I drop my lower dash cover these rubber things keep falling out. I now have three of them and no idea where they go. They must prevent squeaks and rattles somewhere?

 

[gsxr]

I also have a question, every time I drop my lower dash cover these rubber things keep falling out. I now have three of them and no idea where they go. They must prevent squeaks and rattles somewhere?

Hey, I can help with that question! Those rubber pads should be glued to the instrument cluster housing. 2 top, 2 bottom, 4 total. They can also make the cluster more reluctant to extract. Darn things always fall off.

 

[gerryvz]

I also have a question, every time I drop my lower dash cover these rubber things keep falling out. I now have three of them and no idea where they go. They must prevent squeaks and rattles somewhere?

View attachment 163817

They go on the top and underside of the W124 instrument cluster.

 

[nocfn]

...and it stops the squaking of the dash. You can replace them with some longer 2" wide strips of felt and some contact cement. YMMV

 

[luckymike]

RicardoD, very, very nice write up. I have two new ignition switches bouncing around in the trunk for the day that I decide to do this job. You've inspired me, and I might have to move it closer to the top of my list. Thank you!

 

[emerydc8]

STOP THE PRESSES! (old man term)....

@nocfn reached out to me and pointed out a possible alternate method. But it needs to be confirmed @Jlaa. After you drop the lower dash you can try and disconnect the plug from the ignition switch leaving everything else in place. Then jam your head by the gas pedal and you may have access to the three screws holding the ignition switch in. Simply remove and replace the switch with the entire steering lock in position. This would really simplify things and exactly how I did the switch change in a my 1990 Porsche Carrera 4. Something for the next person to try *cough* @Jlaa *cough*.

I tried removing the plug with it in position, but there was too little space behind it to get my fingers on it and pull it off. Now that I know how/where it comes off, I might have been able to slip a screwdriver in there and pry it off but it is really tight back there. The next problem I ran into, even with the assembly rotated partly towards the floor is that I couldn't get a good grip on the three Phillips head screws and one started to strip. IIRC I had to rotate it further down to get a better grip with a larger screwdriver. Of course, I was also unable to replace the breather hose at the bottom of the ETA without entirely removing the ETA (thanks @lowman ), so it will be interesting to see how you and @Jlaa do the next switch.

 

[nocfn]

yes waiting for that ^^^

 

[nocfn]

This ratchet helps in tight spaces as one can turn the wheel or use the lever. The pen is for scale.

 

[geraniumtr]

Ricardo, tks for the very helpful 'How-To' on replacing the ignition switch. I just did mine this evening on my 94 E320 with 302K miles. What prompted me to tackle this started 10 days ago when on occasion the CEL and ABS light would stay on after the car was started for some 20-30 seconds. Not every time I started the car but intermittently. I conferred with the senior vintage car tech at the dealer and after checking battery voltage, ground connections under the hood, the OVP relay, fuses and pulling codes from the diagnostic box it pointed to the ignition switch.

He mentioned it was possible to R & R the switch in situ but I don't see it. If you're a small person with a specialty screw driver and do this for a living just maybe. There's a vent duct in the way plus the screws come out backwards plus you're working blind. I pulled the instrument cluster, loosened the steering wheel and removed the switch per Ricardo's write up. One note... the center plastic slot in the new switch has to be oriented to mimic the old switch. Just stick a screw driver in the slot and turn it CC as necessary.


Regards,


Peter

 

[RicardoD]

Awesome Peter, glad it worked out for you. It is not too bad with the right tools and a bit of patience. Maybe I could do it from underneath. I should try that on @Jlaa car but we have a way of turning one hour projects into 6 hours endeavors.

 

[bclifton]

Definitely nice details on the write up, @RicardoD! I'm trying to see what might be different about your setup versus my 300D. For sure, I don't have the transmission lockout cable.

STOP THE PRESSES! (old man term)....

@nocfn reached out to me and pointed out a possible alternate method. But it needs to be confirmed @Jlaa. After you drop the lower dash you can try and disconnect the plug from the ignition switch leaving everything else in place. Then jam your head by the gas pedal and you may have access to the three screws holding the ignition switch in. Simply remove and replace the switch with the entire steering lock in position. This would really simplify things and exactly how I did the switch change in a my 1990 Porsche Carrera 4. Something for the next person to try *cough* @Jlaa *cough*.

For my setup - I can confirm it's possible (and quite easy) to remove WITHOUT taking the steering wheel or instrument cluster out. If you're taking your time and being careful, it's fine to take the instrument cluster / steering wheel off. Instrument cluster is fairly easy to take out / replace- just those rubber shims can break loose (as noted). Steering wheel is a piece of cake to take off / put back on.

I replaced the ignition switch recently with a new part to fix intermittent circuits turning off (acting like the ignition is off). This worked out perfect! And then more recently (last weekend), I took the ignition out again to replace the vacuum housing that is found on diesels. Each time I did it in just under 40 minutes (time difference calculated when negative on battery is reconnected again after it's all together).

A few of the tricks I do... for folks if they try to remove without taking out steering wheel / cluster:

• Move the driver's seat all the way back
• Move the steering wheel all the way out (towards you)
• Remove the 5mm cap bolt, unplug the electrical connectors (mine has two)
• Put key in and turn key on ignition to position 2
• Grab a hold of the plug on the back of the ignition switch. It's going to be SUPER crammed in there. But you can try wiggling it and with enough patience, it will come loose. Wiggling too and fro, gentling pulling one side of the assembly at a time when you get a firm finger grip. This can take a few minutes to wiggle it out, so don't give up too soon.
• For diesels, you can use a screwdriver to pry the vacuum connectors off
• Push the spring clip in with a screw driver and start wiggling the ignition assembly loose (twisting and gently pulling to the right). It'll eventually go under the metal housing and then you don't need the screwdriver anymore.
• Here's where things get controversial The only way I can get the ignition assembly out of the housing is by pulling it right into the climate box. There is going to be a rubber sheet which you can press into (as gently as possible) and it will give- leaving you with enough space that you can pull the ignition assembly out enough that it finally clear the housing that it's snapped into. Sometimes, I'll put back to position 0 and remove the key once the spring clip is loose to make the assembly easier to grab.

The above descriptions should make sense given all the great pics @RicardoD took

For reference, I am a pretty big guy. Not really tall (6 foot) but I have a pretty big belly area With the seat back, I can usually reach everything laying on my back facing up (door open with feet out).

One pro-tip that is super easy to forget. The trim panel where the light switch is - there's a light bulb that'll be dangling after you disconnect it. When you go to put the lower knee bolster back on, make sure to feed this wiring THROUGH the hole that's left open. Otherwise (like I do almost every time), you have to fish around in there until you find it (when you're ready to put that light switch cover trim back on )

 

[M104-AMG]

Below is a good visual video. Just did mine in under 40-mins.

neil

 

[rwdnp]

I was going to attempt this with the ignition switch in place using the little wrench from Mercedessource but I found the lack of space/access to be a challenge. After following RicardoD's great step-by-step instructions I amazed myself that I got the assembly free (quite a tight fit to get end of the assembly out) but now I'm finding that I can't unplug the wire assembly from the back of the switch. I read that for some models the key needs to be turned in order to allow the plug to be removed but that doesn't seem to be helping free it up. Any suggestions?

 

[emerydc8]

I thought mine was stuck too but squeezing a flat head screwdriver between the plug and switch and separating by twisting did the trick.

 

[bclifton]

I read that for some models the key needs to be turned in order to allow the plug to be removed but that doesn't seem to be helping free it up. Any suggestions?

This is right- you need to put key in the correct position. Put key in, turn it like you're turning it on (with your negative battery disconnected of course). That should allow it to be pulled out. It can be a PITA to get loose though - I had to keep pulling and wiggling side-to-side.

This position might not always be needed - but there are models that have a plastic piece that actually goes into the wiring harness (see picture one). It will only line up properly for removal if you put ignition into the correct position. Some don't seem to have that (see picture two). For picture one, you will not be able to remove the electrical connector unless it's in the proper position.

 

[emerydc8]

I did not know about this. I guess the two switches I replaced--both likely original with the white plastic center tabs--must have already been in the #1 accessory position since the tumbler was removed first and that's the only position that allows removal. Probably why it's not mentioned in the shop manual. My replacement switches had the round black center without tabs. I wonder what the logic was behind the original white center with tabs. It's not like the plug had any room to fall off back there. Good to know though.

 

[Tim]

I would also reference these notes from @emerydc8 , I can't say I totally understand how the steering wheel lock / ignition switch works.

Another Bad Blower Regulator? [Solved: Bad Ignition Switch] | Heating and Cooling (Interior HVAC systems)

This is the extraspecial M119 specific electrical diagram. I marked everything for easy reference. Assuming the PBU is spitting out the correct voltages, you could check fuse F15 or the PK/GN wires leading up to Fuse F15 or even perhaps that same PK/GN wire leading up the contact 15X in the...

www.500eboard.co

emerydc8 notes, must be from service manual:

I had same experience. When I finally had everything back together I was able to remove the key. But initially my key was locked in, I couldn't do the final twist to remove they key from the ignition switch. I re-installed the parking lock valve cable and then I got it to work but it is not as smooth as it used to be. I don't know if that is the new switch being "notch" or something else. I will update if it smooths out.

I have a 1992 400e, where can I buy ignition lock cylinder, dealer says NLA?

 

[gsxr]

See post #232 at the link below... is your dealer checking part number 126-460-02-04?

OWNER Post in thread 'Kridre (400E)'

May 16, 2025

Something is fishy here. In USA, there are 6,000+ of the VIN-coded tumbler 126-460-02-04 in stock and ready to ship. Screenshot below from Paragon, from my dealer.

I wonder if you could order the tumbler from the MB Classic Center in California?

• gsxr

• 
• 

 

[nocfn]

I have ordered 3 tumblers in my career and all 3 came from Dallas/Fort Worth via Irvine classic center.