This will not be an easy one to find. Make sure that everything is turned off. Disconnect the ground cable from the battery. Hook one side of a 12 volt lightbulb like a tailight bulb to the ground cable of the battery and connect the other end of the lightbulb to the negative side of the battery. The light should not come on. If it does, that means that there is a voltage drain somewhere on your car-and that is what is running down the battery. To find out what is making the light come on, you will have to disconnect things one at a time. Start with the radio, then the clock, wiper motor, heater blower motor, etc, one at a time until the light goes out and then you found the problem. Now you see why good electrical repair guys make about $80/hour!! Have fun… Eric