07 Silverado Front Speakers don't work

The front speakers (in door) have been intermittently working. It seems as though when it's damp or wet outside they don't work, and when it it's low humidity they work. I'm thinking it's a short somewhere. I haven't taken the dash or doors apart yet, but that's my next step. I'm a little nervous to tear it all apart, because I don't want to break anything. Any suggestions? Has anyone else had trouble with this make/model doing the same thing?