BMW E46 battery drains overnight: measuring parasitic draw
E46 battery drains overnight: what is a normal parasitic draw?
Once the car has gone to sleep, the parasitic draw measured at the battery is about 20-40 mA. A reading of hundreds of milliamps or over 0.5 A means something is staying on. A healthy battery reads about 12.6-12.7 V at rest.
How do you measure the E46 parasitic draw?
1. Lock the car and wait about 15-20 minutes for the systems to go to sleep. 2. Measure the current with a multimeter between the battery terminal and the clamp (use the meter's 10 A input so the fuse does not blow). 3. Lock with the remote twice, so the interior motion sensor does not disturb the measurement.
How do you find the circuit that draws current?
Pull fuses one at a time while the meter shows the reading. When the current drops to normal, the consumer is in that fuse's circuit. Common culprits are the tailgate light switch and wiring harness, the navigation unit, the heater pre-resistor and a faulty alternator.