[VetteVet]

Connect your mutimeter between the negative terminal and the negative cable of the battery and take a key off reading. The drain should not exceed .003=.005 which is milliamps. Look for any obvious things left on. Pull the alternator charging wire off the back of the alternator and check the meter. It should drop to the readings I posted. If it doesn't then start pulling fuses on circuits that are hot with the key off. Brakes, headlights, emergency flashers, One at a time until the reading drops. That will be the circuit that's draining the battery. Do the other suggestions as well.