1995 Pontiac Grand Am Dead Battery in Morning

something is staying on all the time and running your battery dead over night for example a light

[quote:1315e802b6="dvachon"]Electrical problem
1995 Pontiac Grand Am 4 cyl Front Wheel Drive Manual 114000 miles

I just bought a used Grand Am and for 3 mornings, the battery was dead. After a short charge, the car will start and run all day, but in the morning, dead again. The battery was checked with a battery tester at an auto supply store and they said it was fine. Any ideas?[/quote:1315e802b6]

More info: With the battery connected (after a day of normal driving, fully charged) the voltage is 15.94V. When the engine is running at low idle, the voltage drops to 15.54V. Can the alternator be tested while still on the car?

yes