Just bought an '85 w123 300d turbo diesel parts car and the car has no key or title. Got it towed back back to my house and wanting to see what all (if anything! This car has been cooking in the sun for several years) works. Is there a way to bypass the ignition switch to turn on the electronics only?

Best would be to get a Key cut from the Dealer using the VIN number. Out here they wanted the car there with the registration. Other places are not as strict on the. And, hope that no one previously changed the Ignition Lock Cylinder. With the Key you could turn the Ignition Lock to the proper position, remove the Steering Colum Lock and then the Ignition switch.

I have no personal experience drilling out the Ignition Lock but there is threads on that.

Is the steering Colum locked and the Ignition Switch in the normal position it would be in if you were going to stick the key in it?

If it is like I describe even if you could get the screws out that hold the Ignition Switch in there is a "T" shaped pieced that has to be properly indexed to remove the Switch. (If you had the switch out you could turn it without the key.)

With out having the Key inserted so that you can turn it into the proper position there is nothing you can do without damaging something.

See the attached pic. One method is to cut the aluminum ears off of the steering Colum lock which the Ignition switch holding screws go through. Note that the attached pic is of an earlier version and #7 is the Ignition Switch but on yours and in fact mine the Ignition switch has a formed aluminum tube covering it.

It would be cramped working down there but if you had a wiring diagram so you knew which wire connected to which wire you could peel some insulation off, pierce with a awl or similar item or install some jumper wires with those wire taps so you could feed Positive voltage to the selected wire.

You could relieve some of that cramped working are by flowing the Instructions as to how to remove the Steering Colum Lock when the Tumbler cannot be turned. There is a pin on the lock you grind off.

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84 300D, 82 Volvo 244Gl Diesel

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An alternate method requires that you have a switch (item 7 in thumbnail above) that has already been removed from another car, or obtained online. The harness connector can then be pulled off the switch that is in your car (remove instrument cluster for access), and connected to the separate switch, which can be operated with a screwdriver, as noted by D911 above.
Here is the lowest priced one on ebay:
https://www.ebay.com/itm/Ignition-Starter-Switch-Mercedes-1977-2004-2025450104-New/292344116030?fits=Year%3A1985%7CMake%3AMercedes-Benz&hash=item441111333e:g5cAAOSwcBhWXy4e

That is not what I remember. Mine is a 1984 300D and it has a piece (see the attaché pic) that locks the Connector to the Switch unless the Key is in the same position that you would remove the Lock Tumbler in. The older model years can be different and don't have the lock.

But, I think that was over 4 years ago so my memory on that is not 100 percent.

The attaché picture is the stock Steering Colum Lock I removed from the Car. The rotating T piece and the extended shroud/tube that are not on the earlier models I assumed were increased antitheft devices so that you cannot pull of the Electrical Connector and use it to hot wire the Car.

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84 300D, 82 Volvo 244Gl Diesel

What I want to know is :

How to remove and replace the electrical contact switch, #8 in the photo ? .

I just replaced the lock cylinder as it locked and I had the devil of a time getting it to unlock , not an impossible job by any means but now the key buzzer is dead and I like everything to work .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

There is a couple of issues. On is that depending on which position the locking pin is in the Switch Plunger will be depressed up into the switch which is the position you would need to remove the switch.

Next in the Picture the yellow arrow points to the direction you need to go to move the switch get it out. The red arrows point to an area you need to stick something on each side to depress the springy plastic hooks on the switch.
The old flat wire Bobby Pins that girls used to use when I was a kid would work fine I think.

Since my Steering Colum Lock was broken and I did also did not know at first how to remove the Switch I carefully took a Hacksaw and sawed off the Aluminum retaining lip and the Switch was easily pulled out.

I am looking for some other pictures and will add them to this poste when I find them.

The middle pic shows where I cut off the retaining lip in the red circle.

The last pic is of the buzzer switch showing the plastic hooks that need to be depressed.

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84 300D, 82 Volvo 244Gl Diesel

Experience is with older models; that lock was not present, and based on the pictures of the replacement parts offered online, is not present in the replacements (which makes the replacements universal).

Prying the harness connector out of the switch will result in breakage of the t-lock, the connector face, or both. The amount of acceptable breakage in this instance is a judgement call for the OP.

You have more faith then I do as to what part is going to break whey you pry on it. Also the newer models have a shroud/tube that prevents you from sticking something in between the ignition switch and the connector.

There is a replacement T piece for the newer ones. It is just a metal stamping out of sheet metal. The end that goes into the Ignition Switch has 2 forks and the outer edge toothed so that when you shove it in the teeth catch and of course the T end sticks out.
I can't remember if that replacement T piece came with my new Steering Colum Lock or not or if I just saw a picture of it. But, either way I did not use and T piece.
Note I also pushed the locking plunger of the Steering Colum in the unlocked position and pushed the pin inwards and epoxied that pin so that the plunger would never again lock the Steering Colum and the Ignition Lock Tumbler would never again have to deal with the stress of compressing the Spring on the Steering Colum Lock Plunger.

I put a red X on the protective shroud/tube. The electrical connector is mostly enclosed by the tube.

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84 300D, 82 Volvo 244Gl Diesel

THANX ! .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Well I hope Amphiduck posts back on what he finally did.

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84 300D, 82 Volvo 244Gl Diesel

Sorry for the huge delay on this guys! I pulled the gauges out saw the connector. I now see the locking pin in the middle which prevented the plug from pulling out, but at the time thought the prongs were so corroded that it was seized. With that thought, I took a flathead screw driver and tried to tap the housing away from the body of the switch (near the three screw holes) and in doing so, the metal cracked and gave way allowing me to bypass the tumbler.

Unfortunately the switch is toast, but it did allow me to see what was working electrically in the car (not much!).

Thanks again for everyone's help on this. Mercedes definitely went heavy duty on their ignition switches.

I'll try to remember to snap a pic when i get home.