MarkC, I don't think the wiring junction on top of the steering column includes a switch for the buzzer. The buzzer switch is inside of the steering column next to the ignition switch tumbler. When you put the key in the tumbler, a little pin sticks out of the tumbler that closes the contact points in the switch.
I recently rebuilt my steering column and accidentally broke the little buzzer switch. It is made of plastic with two strips of copper for the contact points and are VERY fragile after 30 years. I didn't like the "dying cow" sound of the buzzer, so didn't even try to replace it.