Principles of Operation
WARNING: This page is about a different car, the 2008 Ford RV Cutaway, 2008 Ford Econoline, 2008 Ford E450 Super Duty, and 2008 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
The horn switch is incorporated within the driver air bag module. When the switch is closed, ground is supplied through the clockspring from the vehicle harness to the horn relay. The horn relay is then energized, supplying voltage to the horns and enabling the horns to sound. The horn relay is located in the battery junction box (BJB).