Classic/Antique Car Repair: 1966 Mustang horn, rainy afternoons, emery cloth

Question
The horn  for my 66 Mustang works...barely.  When I push the horn it almost seems it takes a minute to warm up and then sounds sick.  Is there a way I can take the horn apart and clean it without trashing it to restore it to "good as new" status?

Answer
I have done this many times and sometimes it works and some times it does not. The cover over the working part of the horn is usually just crimped in place. With the horn off and on the bench locate where the crimps are that hold the cover on and with a small screw driver pry them carefully away to loosen the cover. On some units I have used my Dremil tool with a small grinder to clear them out of the way. When I put it back together I use a little JB epoxy weld to set the cover back on. Inside the horn there is a diaphragm, a magnetic coil, and a set of points. When current is applied the magnetic coil pulls the diaphragm down and opens the points. The diaphragm springs back up closing the points and it happens all over again. Most of the time the points are burned causing a poor connection. A strip of very fine crocus cloth (very fine emery cloth) run though the points should clean them. If the diaphragm is broken then it is usually junk as well if the magnetic coil is shorted or open. The coil can be tested with an ohm meter. Test the horn on the bench before closing it up and re installing it. It is a fun rainy afternoons project, especially if it works when you are done.
Brad