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A parasitic draw, also called a drain, is the flow of electrical current that can occur while a car is parked and off.

Electrical systems such as seats, heated seats, brakes, control units, the radio, the clock, power mirrors, etc., may develop a small draw known as parasitic drain. If the power draw goes above normal levels, this can be dangerous to your vehicle's battery life.

Turn of the vehicle, leave doors, hood, and trunk open. Let it sit for at least 15 minutes. Use a digital multimeter and pull fuses one by one. If you come across a reading of around 50 milliamps or higher for any circuit, it may mean you found the parasitic draw. Remember that if you have a large, modern luxury car, its added computerized systems will likely see a couple of circuits pulling over 50 mA current draw which could be normal.

Can a bad ground cause a parasitic draw? 

A bad ground might not cause a battery to drain, but it will prevent it from properly recharging.