General Testing

Horn Tone Poor
1. Harsh tone-caused by loose bolts in sheet metal mounting area.
2. Weak, strained tone possible foreign body in horn that should be shaken out or removed.
3. Weak tone caused by insufficient current.
4. Low pitched moan-caused by excessive current.
5. Harsh vibration-caused by horn contacting sheet metal. Bracket should be adjusted to give horn clearance and freedom from interference.

Horn Sounds Constantly
1. This condition can be caused by sticking relay contacts in the relay or horn pad.
2. Horn relay may be energized by wiring shorted to ground.

Burned (open) windings on most horns are caused by one of the above malfunctions. Before horns with open windings are replaced, make sure that none of the above conditions exist, or the horn windings will burn open again.

Bench Checks
Measure
^ Current draw of the horn while born is operating. Current draw for the horn should be between 4.5 and 5.5 amps at 11.5 to 12.5 volts.
1. No current reading may indicate a broken connection or an open circuit due to a broken terminal or overheating. Most horn problems are caused by the horn being operated continuously, developing sufficient heat to melt the wires in the winding, causing an open circuit. Overheating is accompanied by a characteristic odor which indicates that the horn has overheated and should be replaced.
2. Absence of current can also indicate that the contact points are open and a current adjustment is required.
3. High current, over 20 amps, indicates a shorted horn which should be replaced.
4. A reading of approximately 18 amps for a 12 volt horn indicates a condition in which the contact points are not opening.