What can drain battery overnight when nothing was left on for a 1996 Chevy Silverado?

1. Parasitic Drain: A parasitic drain occurs when a small amount of electrical current is drawn from the battery even when the car is turned off. This can be caused by various factors, such as faulty wiring, malfunctioning accessories (like a glove box light), or a problem with the alternator or voltage regulator.

2. Faulty Ignition Switch: A faulty ignition switch can fail to completely turn off the electrical system, resulting in a continuous drain on the battery.

3. Bad Battery: An old or defective battery may no longer hold a charge and may slowly discharge overnight.

4. Alternator Issues: A faulty alternator may not be properly recharging the battery while the engine is running or may overcharge it, leading to premature battery failure.

5. Corroded Battery Terminals: Corroded battery terminals can impede the flow of electricity, affecting the battery's ability to hold a charge.

6. Faulty Electrical Component: A malfunctioning electrical component, such as a light bulb, fan, or radio, may remain active even when the car is turned off, draining the battery.

7. Trunk or Hood Light Issues: Ensure that these lights are turning off as they should by opening and closing them a few times to check proper activation of switches.

To accurately diagnose the cause of the battery drain, a multimeter or other diagnostic tools might be necessary to measure the current draw and identify the specific component responsible for the discharge.