Draining the Juice!

You gotta get out your multimeter.

1st: Double check that your alternator is indeed charging. Easiest way to do this is to measure your battery voltage before you start the car, then start the car,let it run/idle for 5 minutes, turn on the headlights, and measure the battery voltage again. It should be at least 1volt higher than with the engine off and usually around 14Volts at idle.

If that works and you're sure the battery is OK, then the next step would be to pull off your + battery cable (car off of course), set your meter to read amps (on the 10Amp scale), and then hook your meter in series with the battery cable and the battery. This will route all battery current through your meter and will tell you how much power the car is drawing. With the key off you should see very little current...usually less than 1/2amp. If you see more, then it's time to start pulling fuses until the current drain suddenly stops. That should at least narrow it down to a single circuit for you.