I'm with Greg. If you're testing right on the battery terminals, you should always see battery voltage (between 12.something and 14, usually), whether it's off, on, running, etc. I'm thinking bad battery, but the zero V has me wondering if maybe you have a broken battery post? Since even a dead battery reads some voltage.
You said you already checked the fuses and connections; I would suggest getting the battery tested before tearing into other stuff.
