[G.R.]

The Master switch "could" drain the battery down if it is going to ground in anyway. An Alt shouldn't drain the battery down unless there is a ground issue, where battery power is being siphoned off due to a faulty ground--rare occurance on an alt.
Try charging your battery then remove the neg terminal from it--let it sit overnight or for a day then hook it up--if it shows a near full charge battery is good--if it is dead, battery is dead won't hold a charge---if it is a good battery and dies there is a ground fault drain on it from your wiring.