Otto,
The horn is hot all the time.
Does the ice pick style test light you used have a light in the handle? If so, you are using the wrong one unless somehow you ran voltage through the wire. If you do not have a volt?ohm meter, you could put 6V on the end of the wire and then ground your pic and touch the brass bearing with the pick end and if it lights up you are good. Try both wires because only one goes to the brass bearing.
Harold
