Here is the address for a paper that is written around a 1969-1974 Chevelle and Camaro horn diagnosis.
It is somewhat generic but it should give you some good tips on locating the cause of your problem.
Also, the paper references some other papers that I authored. Those papers can be found at:
Click on Jim Shea's Steering Papers
Click on A & F-Car Steering Papers
Scroll down to the Standard (non-adjustable) Steering Column section
Or scroll down to the Tilt Steering Column section for additional papers and pics.