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Must be ignition switch under steering column, but..................
Might be because the Actuator Rod is not working correctly
This is a general diagram of how system works:
https://blazerforum.com/forum/attachments/full-size-k5-1969-1991-gmt415-1992-1994-tech-42/11046d1357121213-ignition-lock-issues-rod-issues-2012-03-08_031156_steeringcollum_diagram.jpg
Turning the key does NOTHING electrical, its all a mechanical operation, to unlock steering wheel and to MOVE the ACTUATOR ROD forward and backward, and that is what moves the Ignition switch into its 4 positions, ACC OFF RUN START
On the back of key cylinder is a gear that moves a rod that moves another rod that moves the ignition switch
Simple, until its not, lol
So pull out ignition switch, looks like this:
https://i.ytimg.com/vi/KK2uO_xaDKA/maxresdefault.jpg
See the pin his finger is on, thats what the Actuator Rod moves into the 4 positions
Once its out connect wires back up and you can move that pin into its 4 positions just to confirm ignition switch is working, i.e. turning off power in the OFF position
If so then hold the end of the Actuator rod under steering column and turn the key to see if there is any "play" in the Actuator rod, shouldn't be off course or you would have what you have now, 4 positions are not precise, ignition switch is not being put in the OFF position