Before you pull the alternator:

1) Disconnect the negative battery cable
2) Make sure everything in the vehicle is completely shutoff and all doors and the trunk is closed.
3) Connect an ammeter between the negative battery cable and the negative terminal on the battery.

The reading should be not more than 80 milliamps. Probably less than 50.

If the reading pegs the ammeter, then look around, again, for something that might be on, such as a dome light or a courtesy light.

Make the test again. If the reading is above 80 milliamps, disconnect the wires to the alternator.

Make the test again. If the reading is now below 80 milliamps, you have confirmed that the alternator has the leak.

If the reading is still above 80 milliamps, then you have determined that the problem is NOT the alternator and you need to start pulling fuses to find the circuit that is causing the problem.