You're right (assuming you have 3.1) that you don't hear a click -- it isn't a switch that merely opens or closes a circuit. Instead, you've got a potentiometer (or rheostat -- I can't remember which term goes with which) that varies its resistance with rotation of the shaft, so there's no click sound.

I'm afraid I don't know about adjusting it, though -- you'll have to wait for someone expert in them to advise.