Aside from just replaceing the horn you would need to put a meter on the horn connections to determin if it was consistantly getting 12 volts from the horn buttons. If the voltage was always there when the buttons were pressed and the horn sometimes didn't work then it may be the horn. Although you would also heed to determin if the horn ground and power connections were good. If the voltage was sometimes not there when the buttons were pressed then it could be a number of items including the button contacts. There is also a spring loaded pin that makes contact with a ring inside the steering column. This may be dirty. You can get to it by taking the plastic cover off on top of the column. Just two screws. Sorry, these electrical things are not too easy at times. You seem pretty handy. There may be an inexpensive horn available at the local Pick-A-Part wrecking yard if you have one nearby. There are always lots of 740's.