key and ignition switch will not turn
 

1979 450SL

my Key started sticking a couple of weeks ago and i ordered a new one and it did not help. the keys work in every other lock but the ignition.

any advise on quick fixes? is it mechanical or is there any electrical that could be wrong? the steering wheel will lock in place?

help i have been stuck for some 15 min before it worked and need to fix it?

are there instructins anywhere on how to replace if that is what i need to do?

lets hope its just the tumbler, there is nothing electrical. The tumbler is removable and the only real fix is getting VIN to dealer to order new tumbler and key, may be some after market but doubtful. Since they are not servicable (as far as I know, but may be - others may be of assist here) once you get the tumbler we can walk you through how to R/R

turn the steering wheel left and right while trying to turn the key, thats the first step before you attempt to change the tumbler.

The steering wheel lock might be binding or jammed. Some lock lubricant might be needed in the tumbler as well.

I will probably get flamed here but I do not recommended lubricants on wafer type MB lock cylinders. The tolerances are extremely close.

I agree with that, but I would go ahead and replace the lock mechanism. It's not hard to do if you can turn it but the lock is a bit pricey (~$80 if i remember from the dealer). Your problem is that if you can't get the key to turn, you are screwed, so I would order the cylinder, and then try as hard as you can to get that cylinder to turn once more - wiggle it, tickle it, vibrate it, try different keys, just get it to turn once and don't lock it again. You have to turn it to ACC or thereabouts to line up the holes in the cylinder and stick a heavy paperclip in there to unlatch the steel collar and unscrew it, then the key cylinder just comes out and you can replace it.

All my Mercedes had the lock cylinders fail at some point, for whatever reason - cheap key blanks, heavy keychains, who knows. I got them all replaced without too much trouble and got new factory keys from the dealer for them- it was expensive but at least I wasn't locked out of my car.

The only lube recommended is dry graphite dust. I agree that it's a mistake to add oil or solvents.