Test the horn by connecting battery voltage to the 1 terminal and ground the 2 terminal.
The horn should make a sound. If the horn fails to make a sound, replace it.
After adjustment, apply a small amount of paint around the screw head to keepit from loosening.
Remove the horn relay(A) from the engine compartment relay box.
Check for continuity between the terminals.
There should be continuity between the No.1 and No.2 terminals when power and ground are connected to the No.4 and No.3 terminals.
There should be no continuity between the No.1 and No.2 terminals when power is disconnected.