[Stocker]

It's been too many years since I had mine apart.... but grounding that copper button will operate the horn relay, which of course blows the horn. The horn doesn't blow when you push the copper button because your finger isn't grounded. If you touch the button with a test wire connected to ground, the horn will blow.

That doesn't exactly answer your question..... just trying to help you with a bit of info. The brass ring on the cancelling cam is getting grounded, which then grounds the copper button.

What dcasalena said about shortening the cancelling cam pin might be right..... it kinda rings a very faint bell with me, but like I said it's been way too many years.