Why is my 2001 Crown Vic draining the battery?

Follow the red wire(smaller one) from the battery to where it meets the red wire from the alternator. At this point, probably near the main engine fuse box, there will either be a fuse or fusible link. Check to make sure not burnt out. To test: Use multimeter and touch red to red and black to black on battery and get a read. Then touch black to black on battery and red to the wire from the alternator on the other side of the fuse or link. If the read is zero the fuse or link is bad and needs replaced. Do this with the vechicle off and at least some charge in the battery. Other possibility is a parasitic drain from a frayed or corroded wire possibly on the starter's wire.

SOUNDS LIKE THE ALT IS NOT CHARGING ENOUGH. WHO TESTED IT AND WHAT VOLTS WAS IT PUTTING OUT AT IDLE AND UNDER LOAD

Then the alternator or internal solenoid is not working.

Check to see if any of the voltage is getting to the battery. If you put a multimeter on the battery while running you should get more that 12 volts should be around 14 volts if so the fuseable link is fine. For one a alternator doesn't have a solenoid in it so I wouldn't trust anything that person said. Since you had the alternator tested and it was good it has already been load tested so that is a incorrect answer as well. You have a new battery but that doesn't mean it is a good battery so have it tested but most likely it is fine. So that narrows it down really fast only one more thing can draw the battery that fast and can do it while you are driving and that is the starter! I'd say you have a starter that is grounding out inside.