DADS50: Do you have a horn relay? Usually mounted to the voltage regulator. That might be the problem. You should have volts on the horn. The button on the wheel is the ground. So volts on the horn? Volts at the relay (if you have one) and volts at the plunger. One step at a time. And if the relay works again if you have one and the horn button makes a good ground then all that is left is the horn. And it made noise so it could be adjusted. There is an adjustment inside that can be made if it just gives a "bark" and quits you can try that.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm1233.htm

Steve H