I tried it on a 12 volt 180 amp battery same click nothing more. No adjustments at all. It's off a six volt vespa. I think it is probably locked up. Just as soon as I hear from him I'm either going to send it back or open it. I have no idea what is inside but I'll know in a couple of days I expect.Hi Deacon,
Probably not enough voltage. You might try connecting two 6 volt batteries in a series circuit to produce 12 volts (if you have an extra one lying around).
Does the horn have an adjustment screw on the back of the housing? I've had similiar issues with some vintage horns...in which the diagragm had to be set just right in order for it to vibrate loudly.