Alternator not charging

Just wanted to say thanks, I narrowed it down to the Number 3 fuse, now to figure out what all is on that circuit and fix it.

So I found a wiring diagram for that fuse, the first thing in line was the under hood lamp, with the test light on, a slight wiggle of the lamp caused the test light to flicker, so I unplugged the bulb and the test light dimmed. So i'll leave it unplugged till I can get the mercury switch replaced. Im having a hard time finding information on how much draw the truck should have on the battery while the key is off, right now it measures 3.30v that still sounds high to me but I really have no clue.

I forgot to hop back on and thank you BMRFIXIT. Ive left that bulb out and the battery has been fine. I did a weekend test without starting it. It just fired right up. I may get around to replacing that switch but I keep 2 flashlights in the truck so it should be fine without it for now. Thank you again for your help!