Measure the current draw of the horn while the horn is operating. The current draw for each horn should be between 4.5-5.5 amperes at 11.5-12.5 volts.

A lack of current may indicate a broken connection or an open circuit due to a broken lead or due to overheating. Most horn problems are caused by the horn operating continuously. This develops sufficient heat to melt the wires in the winding, which causes an open circuit.

A characteristic odor indicates that the horn has overheated and should be replaced.

A lack of current can also indicate that the contact points are open, requiring a current adjustment. High current, over 20 amperes, indicates a shorted horn. Replace the horn. A reading of approximately 18 amperes for a 12-volt horn indicates that the contact points are not opening. This condition requires a current adjustment.