The ignition switch on my 85 300SD went bad, it felt "loose" all of a sudden
(like no detent where "power ON" should be, and would not turn the starter
on.  I rigged up a battery power on/off switch and a separate switch to
engage the starter to keep it going until I can replace the ignition switch.
I still have to insert and turn the key all the way to the right to unlock
the steering wheel,  and because of the vacuum line start/stop control. I
found a vendor that  will supply a new ign key and cylinder for
$38.00....but the ign housing is $128.00! (ouch!!!!) Question is, are the
electrical contacts and switching function all in the housing....could I
transfer the original key cylinder into the new housing? Or could it be
solely  something that has broken on the cylinder that is not actuating the
switch mechanisms in the housing? Don't know if I need one or the other, or
both.