This is based on my recent adventure changing the glow/starter switch in my 1987 300D Turbo (W124, OM603). Removal of the steering lock and the glow/starter switch is covered in detail with pictures. I have assumed that you can get your key into the lock and turn it to "position 1." If you have lock cylinder problems, this thread will not help you.

It took a good while to find the instructions in the FSM because the ignition switch is considered part of the steering lock mechanism, so it was placed in the "Body" section under "Steering," where it is section 46-8010 (5 pages), "Removing and installing the steering lock complete."

Although the FSM says in this section (bottom of the fourth page) that the ignition switch can be removed with the steering lock still in the car, I do not advise it. It's easier to remove the steering lock and switch as a unit.

You do not have to remove the steering wheel although access is a little easier when it is out. If you do remove the steering wheel, be careful not to damage the combination switch or the cruise control switch as they no longer have the wheel to hide behind. The airbag is held on by T30 Torx screws (access through two holes in back of the steering wheel). The steering wheel is held on by a 10 mm Allen screw that is very tight and also has blue Loc-tite ® on it. Make sure the car's wheels are turned dead straight ahead and note the position of the steering wheel so you get it back in the same place.



First step in all cases is to disconnect the negative battery cable and make sure it can't accidentally touch the battery post.



If you choose to remove the steering wheel and airbag, you must go into the front passenger footwell and unplug the red airbag connector.



Now unscrew the two Torx screws, lift off the airbag, and unplug its little red connector. Put the airbag away in a safe place. Loosen the 10 mm screw in the center of the steering wheel. Use the steering lock to keep the wheel from turning (FSM advice) and use a good-quality Allen socket with a short extension and a long bar. With the screw out, the steering wheel will pull off easily. While you have the steering wheel off, check and clean the contact rings in the wheel and the carbon brushes in the steering column. Put the steering wheel away in a safe place.



Now remove the driver's lower dash panel. You will then be able to see the steering lock. The ignition switch is all the way forward on the assembly and very hard to see. Put the key in the lock, turn it to position 1, and use the home-made wire tool described in FSM 46-8010 to remove the lock cylinder. Note the diagonals cut on the tips of the wire -- they are critical. Put the key, lock cylinder, and wire tool away in a safe place just as you removed them from the steering lock assembly. From this point on, do not turn anything in the lock assembly.

The next picture was taken from underneath.



Pull off the plug at the back of the glow/starter switch. There isn't a lot of room back there but you should be able to get the plug loose and out of the way. If you have a later model W124, there will be a transmission lock cable that you will have to remove. FSM 46-8010 shows it but my car doesn't have one so it's not in my picture. Also disconnect the connector(s) for the warning buzzer. (This is the alarm that tells you that you have left the key in the ignition.)

The FSM now wants you to remove the vacuum hoses that shut off the engine in diesel models. However, I found them really hard to see, much less touch, and decided to loosen the steering clamp first. Therefore, I used an Allen wrench (I think it's 4 mm) to loosen the clamp (you don't need to remove the screw). Press in the locking pin using a small screwdriver or pin punch and twist the steering lock while pulling it partly out of the clamp so you can get at the two plastic vacuum hoses. Pull the rubber connectors off of the vacuum switch, making sure you remember which line goes where. The brown hose goes outboard, the brown/blue hose goes inboard. The rubber jumpers are not color coded.

With all that stuff off, the lock assembly is ready to come out. I had always wondered why the climate control air box had a rubber section. I now found out why.



The steering lock mechanism is so long that to get it out of the jacket tube you must push it well into the air box. You don't need to remove the rubber piece but it requires some pushing and wiggling and there is barely enough room to get it out. FSM never mentions this, of course. Once you get the mechanism out, you can lay it on your work bench and it looks like this picture. Resist any urges to fiddle with the innards of the mechanism.



Now you can remove the glow/starter switch from the lock assembly. Hold the lock (it's convenient to put it in a vise using a rag to prevent scratching) and remove three slotted screws. The switch will lift out and should be covered with white grease. Scrape off some of the grease to put on the new switch, then toss the old one. One final warning: the FSM says that if you try to turn the steering lock mechanism with the switch removed, a detent in the lock mechanism locks in such away that it cannot be unlocked. Take heed and do not fool around!



Notice that the switch has two rounded "corners" and one square corner as well as a locating protrusion that fits into a matching notch in the steering lock. The new switch must go in just as the old one came out.



Remember that the old switch came out in "position 1" so the new one must be in the same position to go in. The picture shows the "face" of the switch, the part that goes into the steering lock assembly.



With the switch turned to "position 1," apply the white grease you removed from the old switch and put the new switch into the lock such that the protrusion goes into the notch. Insert and tighten the three slotted screws. Leave the mechanism in "position 1."

Now wiggle and squeeze the lock mechanism back into the jacket tube, compressing the locking pin with your fingers until it goes into the tube. Reconnect the vacuum lines and push/twist the mechanism until the locking pin pops out of its hole. Notice that there is some rotational play in the lock assembly. Make sure that the locking pin does not bind in its hole and also that the lock is lined up so that the escutcheon will go over the lock cylinder when you put the lower dash cover back on. I found that "tilted down a little" is the preferred way but I had to remove the lower panel again to get it right.

With the steering lock back in place, tighten the clamp, reconnect the buzzer connector(s), reattach the cable to the transmission if you have one, and put the big plug onto the new glow/starter switch. Notice that the lock assembly is still in "position 1."

Now retrieve the cylinder lock with the key and special wire tool still in it, and carefully put the cylinder back just the way you took it out. Once you are sure you have the cylinder all the way in, remove the special wire tool. While holding/pushing the lock cylinder in with one hand, try turning the key a little to see if it "feels right." If it does, see if the key will turn to "position 0" and come out.

The lock cylinder now should be firmly in place and you should not be able to pull it back out. If you can, you didn't push it in far enough. There's a little detent that must line up between the lock cylinder and the steering lock mechanism. I had a hard time getting it to engage the first time but with some patient wiggling it went all the way in and the lock locked in place.

Once the lock is firmly seated, you should be able to insert the key and turn it through its various positions including "start," which should be spring-loaded and should have a non-repeat function (you must turn the lock all the way off before it will go into "start" again).

With that, the hard parts are done. You still have to put the lower panel back and reattach the steering wheel and airbag. Wire brush the big screw and use fresh blue Loc-tite ®. The little red airbag plug must audibly snap back in place (it has a built-in short-circuit link that you are pushing out of the way -- see FSM 91-660 for details). Plug the red connector in the passenger footwell back together and replace the floor panels. Now reattach the battery negative cable.

With everything back together, you should be able to insert the key and start the engine. Make sure the SRS light comes on for a few seconds and then goes back off. Turn the steering wheel lock to lock a couple of times. Make sure the turn signals cancel, the horn works, and the SRS light does not flicker. You're done!

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Nice. Looks pretty similar to 123.

Excellent guide, Jeremy.

I might have to give it a try when I'm back home

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1982 240D, sold 9/17/2008
1987 300D TurboW124.133 - 603.960, 722.317 - Smoke Silver Metallic / Medium Red (702/177), acquired 8/15/2009
262,715 and counting

Great write-up and pics Jeremy - I wish I had seen that before I struggled with that job about 15 years ago. In my case I had to replace the short shaft (tongue and slot) that connects the lock tumbler spade through to the switch - the lugs had broken off in the switch! I was surprised to discover that they had used the same alloy material as the body for that little shaft and have since then been gentler with the key when starting. I had to destroy a lock mechanism from a P&P to replace it. A new lock is serious $$$.

Some years later I did have to replace the switch and decided to try to remove it with lock in place as per FSM. Removing the three slotted screws with a screwdriver was a pain so I replaced them with M4 x 15 Allen cap screws and then refitting was a breeze with an Allen key.

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Beagle

Using Allen cap screws in place of the slotted screws is a great idea, Beagle. Hopefully I'll never have to replace that switch again and won't have an opportunity to regret not doing so myself.

A lot of that assembly does appear to be made from some sort of pot metal, which surprised me. Certainly not as strong as it should be.

Replacing the entire assembly would indeed ruin the kids' Christmas. When I replaced the cylinder lock two years ago it was about $100 from the dealer. The switch was under $40 from an on-line supplier. The rest of the assembly -- steering lock and all that -- is (I just searched) about $100, depending on the supplier. So figure about $250 for the parts if you do it yourself.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Hey - haven't been back here for a while... Guess what happened to me last night?

Yep - key no turn. Stuck in the off position. Steering locked. Had to get a tow.

I'm pretty sure the tumbler is worn to the point of no repair and I'm willing to sacrifice the whole key assembly. I JUST NEED TO GET THE STEERING UNLOCKED.

Is there a way of going at this thing so that I can pull the pin from the column.

I am not afraid of big sharp tools that cut metal.. I just don't want to double-bugger my odds or make it worse for myself.

Is there a help / how to on this?

__________________
Cheers!
Scott McPhee

1987 300D

Don't start drilling until you exhausted all other options. Stick the key in the ignition is use a handheld sander or something else that vibrates to try to jiggle the tumbler free while the key is in the ignition. Guys have had success doing that before.

Power tools are for extreme situations. I don't think you are there yet.

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'80 300SD - '83 240D - '00 E55 AMG - '02 G500

Tried all keys, some hardly used and not worn.. no difference, tumbler won't tumble.

Will give vibration a try.

Do you think it's generally safe to blow (90 psi?) compressed air into the ignition key hole to get rid of dust or debris?
.. followed by a few key insertions and vibration with key inserted... would be my approach.

I know you're supposed to use dry or suspended graphite for locks.

However, at this point my goal is to get ONE GOOD TURN and get the tumbler out. Once out I can clean it properly, dry it and use graphite.

For now... just to get things moving would a shot of brake cleaner help? Or got to WD40 directly?

__________________
Cheers!
Scott McPhee

1987 300D

OK sad to report...

All the lube spraying, key jiggling, vibrations applied, compressed air shots, key jiggling, twisting, niggling, up/down side-side, slight variations in key insertion depths, slight tensions on tumbler while twisting, hard pressure twists, even turned the car upsidedown and tapped the tumbler with a hammer thinking gravity was holding something down... has all resulted in KEY NOT TURNING.

Just kidding about the car upsidedown thing. But it crossed my mind.

I now have a very clean key and I'm sure all the black has been spray lubed out and blown clear of the tumbler.. so it's probably a very clean and new looking mechanism in there but alas is broken somehow.

Now the fun I guess.

I want to turn the tumbler and hopefully get it out. Thinking there must be a way to mechanically damage it using power drilling or grinding tools in such as way that I'd be able to rotate what's left of it to emulate a key turn enough to get it extracted. Can this be done without damaging the whole lock mechanism?

I want to get the steering column unlocked. I am hoping that a turning what's left of the tumbler is enough to retract the locking pin in the column. I saw online somebody dropping steering column bolts and using a grinder on w123 to grind off the locking pin. Is something similar possible on w124?

My car is sitting there with windows rolled down and covered in plastic because it's raining, and right now I wish I had crank windows. Haven't had a moment to figure out how to electrically short the motors to wind them up.

I guess, essentially, I'm looking for advice on doing this repair from people who have gone through it on w124 and came out the other side.

Of course, I understand "how to break ignition key security" is not a topic we like to post about on internet. If you'd be so kind as to PM me with pointers instead of posting to this thread, totally get it. And much appreciated.

I've been a member here for a decade so please trust me, this is my car I'm talking about.

__________________
Cheers!
Scott McPhee

1987 300D

I think I found the jackpot post... thanks Whunter

__________________
Cheers!
Scott McPhee

1987 300D

Got a link to the jackpot?

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Check out my website photos, documents, and movies!

Oh, it was just a sticky list on this forum about this subject, put together by whunter.

Leading to the most premium informative post from Mark who describes so clearly the game in getting the black collar off the assembly so you can get at the key tumbler / cylinder. Appropriately titled God Has Spoken Re: w124 1987 300E Lock Cylinder Tumbler


But even so clearly and carefully understanding the theory and operation of the internal latches that keep the collar on, and use of bevelled pins of exactly 2mm dia trying to unlatch my collar ... it would not. I deduced there must be some internal interference / debris keeping my pin tool from engaging the dogs as it should. So I resorted to grinding the collar off. There's a technique I can share here about doing that to make it go smoothly with minimal collateral damage.

__________________
Cheers!
Scott McPhee

1987 300D

There are many many key stuck / won't turn / my ignition cylinder lock is fragged threads and posts on this forum, I don't know where best to post this advice and don't want to start yet another thread.

My car is 87 300D so I have an affinity to this thread so allow me to post here..

This is THE "remedy" for ANY key situation (missing, broken off, won't turn, can't pull out, etc.. etc) and ANY ignition key cylinder issue (can't insert key, key won't turn, key stuck in any position, cylinder implosion and crumbled, etc..) once you have exhausted your patience or ability of correctly using pins to eject the collar and cylinder and you are getting nowhere... and the clock is ticking and you got to get the steering column unlocked and/or car started...

By now you have dropped the knee panel and removed key bezel/trim ... if not do. You do not have to remove steering wheel, instrument cluster, or any other trims. So now you're looking at the whole naked ignition lock mechanism with that bloody black collar wrapped around the tumbler. It's coming off not as designed.

Using pair vice grip pliers locked around the collar and begin rotating by rocking motions side to side, keep doing it more forcibly until you break the single tooth cog made of pot metal that acts to index the collar preventing it from rotation. Now the collar is free to rotate. It will spin indefinitely and is not threaded. Remove pliers see if you can spin with finger strength, if not get stronger fingers and or give shots of lube into the tiny holes on the key face and key hole. When the collar spins round again to original position the tooth cog remnant likes to make it rest there, having to use pliers again to nudge past that point to spin again for the rest of the trip.

Use an air tool die grinder with a 3" cut-off disc with protective shroud surround, as shown, to make quick work of this.
Open the front doors to let smoke out.
Have an extinguisher nearby.
Wear protective face shield and ear protection.

Hold the tool stationary alongside the collar so the disc is meeting the collar's cylindrical side, about 1 inch from the key face side / half inch from the collar's base. Tool spin axis is parallel with key turn axis. Goal is to grind a groove around the collar by spinning the collar. The front half of the collar (inboard, key side) will fall off leaving the base of the collar (forward, outboard, engine side) on the assembly.
Spin up and begin slicing a groove around the collar in light passes as you turn the collar, keeping tool stationary, grinding deeper in successive passes, until the collar splits in two pieces and front falls off.

The tumbler is now free to be pulled out using needle nose pliers or whatever, give it a yank. Using a pin tool in what would be the 2 o'clock pin hole will press the spring clip in to help get the tumbler out. Or just get manly on the damn thing and it's coming out.

There can very well be bits of debris in there to extract next with tweezers or needle nose... NOW you can see the dog latches holding the back half of the collar in place. Use picks to pull those inward and the collar remnant easily comes off.

So a new tumbler with key and a new collar is required if you want to get the car to OE shape. I don't know of buying just a new collar, and not dropping dollars on a MB part if it's more that $10, so I'll design and 3D printing a replacement made of plastic. Yup plastic, shhh don't tell anyone. And it will NOT use those dogs and internal groove to hold it on, but will be held in place some other easy way.

But first, I'm thinking I'll pull the mechanism from the steering column (like this thread so kindly outlines) and defeat the steering lock pin so that never happens again. Probably just grind the lug pin off the tip of the mechanism that inserts deep into the column.

Attached Thumbnails

 

__________________
Cheers!
Scott McPhee

1987 300D

Don't be like me and reverse the two vacuum lines on the ignition switch... Doh!

Issue and results and correction documented here:

Scott reverses the vac lines on the ign switch

__________________
Cheers!
Scott McPhee

1987 300D