I just had a problem with my ignition switch and want to give some helpful advice to others so you won't have similar grief.My 300d has 223,000 miles on it and several times (not very often) the key would not turn in ignition,but I was always able to make it work by jiggling the steering wheel..until last time!No amount of jiggling ,light tapping,heavy tapping,or even the locksmith,could get it to move.
If this happens ,and you do your own mechanic work like me,save your money ,don't call the locksmith.Better to have it towed home and you can easily remove the whole lock/ switch assembly in less than 1 hour. After checking this forum for others having ignition switch/starter sticking/ no key return problems,let me advise you to replace your whole ignition assembly while it is still half working or it will leave you stranded when least expected.
Steps to remove ignition assembly when key won't turn at all.
1.Remove the instrument cluster.
2.Remove the panel under steering wheel.
3.Remove the two vacuum lines attached to switch.
4.Remove the two small nuts from steering column bracket directly above the rippled steering tube section.
5.Remove the allen head screw right below previous mentioned bracket and use a flat blade screwdriver to pry open and loosen the clamp.
6.Remove the chrome trim ring from around the key hole.
7.Remove the 2 large nuts from the upper steering column bracket.These are just below where the instrument panel sets.
8.Pull down on steering wheel first to get screw studs in step 7 out of stud holes (about 1 inch),at the same time pulling out on dash piece to allow face of key hole assembly to clear and drop behind it.
9.Pull up on steering wheel just enough so bottom column bracket clears the studs (step # 4) and carefully let the steering wheel drop to the seat.This will allow you easy access to remove the wires from the back of ignition switch.
10.Center punch and drill out the pin in the steering column ignition switch holding tube and WOLA! the whole ignition assembly pulls straight out.I was surprised at how soft the pin metal was as compared to the key tumbler assembly metal,which broke every bit the locksmith tried.
After careful examination of the entire ignition assembly ,I noticed 2 of 3 screws that secure the switch assembly to the back were totally loose,leaving the switch part very sloppy and separated 1/4 to 3/8 inch from the main body.My theory is, this caused the key not to turn, and may be the cause of a lot of other similar model ignition switch problems.