^agreed, if the horn works for some uses but not others, then it is not a wiring problem.
i have seen a horn or two go bad but it would make noise after it received power for a second or two, but would not make any sound for short pulses less than a second.
in one of the cases, the horn did sound very inconsistent. not like one of the horns were shutting on and off, but the tone to the horn itself kinda fluctuated higher and lower in tone and also the level of the horn went up and down a bit.
i think this was what joe was getting at when he asked if the horn was instant or had a delay in it.