Boat Horn inner workings

[robertmee]

Okay, I'm feeling dense as I don't quite understand how the internal mechanisms of a working boat horn are supposed to operate. The horn in question is similar to this:

http://www.firstchoicemarine.com/p-1...orn-10035.aspx

Mine is not working so I took it apart. I get how there's a magnetic coil inside that vibrates a disk against another disk to create the chatter. What I don't get is mine has a small make/break contact above the Negative side winding. It's made by tension of the contact spring only. I don't see what could break it and what function it would even serve.

I have good winding resistance on the magnet, so the coil is good. What I don't have is continuity between the Common side connection and the common side magnet lead. So, obviously, the magnet is not firing. I actually got it to fire one time, but none since. But I don't know the path from the common connection to this magnet lead. It goes through a stacked electrode with an insulator between this contact and the winding. Unless you've taken one of these apart, none of this may make sense, so I'm hoping someone has taken one apart before and sees this.

Anyway, I hate to buy another one for $25 + Shipping if I can get mine working. Plus it is original to the boat which is always a plus to me.

EDIT: Eureka moment. Okay, I think I understand the purpose of the contact. As the disk deflects due to the magnet, it opens this contact, releasing the disk which makes the contact. Rinse and repeat which gives the chatter. Makes sense. So, I guess for some reason, I don't have continuity between the magnet and the negative contact. I wonder if the gap on this contact is too great or corroded. Time to get out the emory board.