Cannot insert key in ignition! (W123)

[mfripp]

I have a 1981 Mercedes 300D, which I've owned for about 3 1/2 years. I've never had any problem with the ignition lock, but suddenly today I found I can't insert the key into it. It goes in about 1/4" and then something blocks it.

I poked around inside the keyhole, and it looks like there are two moving pieces of metal just inside the key slot -- one on the left/bottom side, and one on the right/top side. The one on the left sits nicely out of the way. But the one on the right seems to have come loose. I can see a worn, straight edge, which looks like it's where the key normally moves past it. Then, further in, I see a semi-circular edge, which is blocking the key from going down further, into the pin mechanism. I can push this piece of metal around with screwdrivers and wire, and even get one corner of it to almost protrude from the key slot. i.e., it seems to be floating around freely in there, as much as the space and its shape will allow. But I haven't been able to pull it out.

Any idea what the pieces of metal on either slide of the key slot are supposed to do? (My guess is that they guide the key into position, and may also be part of the mechanism that keeps you from removing the lock without the key.)

Any idea what I can do to get the key working again? Should I try to drill this loose bit of metal into little pieces, and pull it out? Should I tow the whole thing to a mechanic and get a new lock?

Any advice would be greatly appreciated!

P.S. In case it sparks any ideas, I should say that this problem started immediately after I had repaired the hazard blinker and instrument cluster lights.

I removed the hazard switch, inserted a piece of paper to keep the electromagnet from sticking, and reinstalled it. Then I tested it a couple of times (which involved turning the ignition to "on", testing the blinkers, then repeating).

I also removed the instrument cluster, soldered some wire to the back of the instrument light dimmer switch to bypass it, then reinstalled the instrument cluster. I connected the electrical wires to the instrument cluster and turned the ignition on and off a couple times, to make sure the lights were working. Then I fumbled around for a while to reconnect the speedometer cable, which involved a lot of reaching up and around the ignition assembly, behind the dash. This may have pushed back one of the vacuum cables slightly, but the ignition switch is so firmly mounted that I doubt I could have done anything significant to it during this process.

Once I had finished reinstalling the instrument cluster, I wanted to start the car up to test everything, and that's when I found I couldn't insert the key. The timing is strange, but I think it is purely coincidental. Maybe the switch was ready to fail, and using it 4 or 5 times in a row pushed it over the edge. It's frustrating, because I was looking forward to having working dash lights and reliable blinkers, but now I can't use the car at all!

Thanks for any help you can give!