1994 Explorer Light Problems

1994 Explorer 4X4, 100000 miles, 6cyl 4L
My symptoms are that pulling the light switch out results in the lights not coming on. Jiggling the switch inward very slightly would allow the lights (including dash) to illuminitate, but a bump in the road could undo it. A mechanic "did something in the steering column" and the lights worked for maybe a month. I have replaced the light switch with a brand new one and a junk yard one resulting in the same behavior. I have been told this is common but have yet to find an answer to this.