I just bought a used ford ranger (2000) and the horn will sporadically beep whenever it feels like it. The truck is not running when this happens. Its not the alarm because they are not steady beeps. The beeps are random and seem to happen most of the time when its raining or damp out. The dealer changed the horn and they say the relay was changed. Can it still be a bad relay, or is there another thing I can check. I'm not too popular with the neighbors lately because of it. HELP PLEASE.

Sounds like you have a wire shorting somewhere. Follow the wires from the horn and look for worn insulation.