If electric horns sit idle for a very long time, their contact points inside can become corroded and cause non-function. A quick repair is to deliberately ARC a power supply wire directly from a battery post using 10 gauge wire or larger. Make sparks fly on the battery post by dragging the connected wires across the battery post. The intermittent high amp flow surges through the contacts, and often burns off the corrosion on the points without need to physically file the points. We call this operation "Striking in a horn". It works most of the time. This set required physical filing of points. 6 volt horns operated on 12 volts are very loud! Minor points adjustment from "Tuning screw" on the back dialed in the best sound.