Horn Problems

[musicfan4322]

I have been having problems with my horn for about a week now. The other day with my 72 C10 was off sitting in the garage and the horn began going off. I disconnected the horn and the next time I went out to my truck the battery was dead. I charged the battery and began trying to figure out the problem with my horn. I changed the horn relay and the problem did not go away. I disconnected the horn button and connected everything else up and the horn still went off on its own. What could cause this problem? If your answer is a short what is the best way to tackle this type of issue from a short?