BMW E39 battery drains overnight (parasitic current)
E39 battery drains overnight - how do I measure the parasitic current?
1. Set a multimeter to the DC range (about 10 A) in series between the battery negative terminal and the clamp, with the ignition key off. 2. Lock the car and wait about 15-30 min for the systems to shut down. 3. Pull the fuses one at a time until the consumption drops. The circuit that was leaking is then found.
How high may the parasitic current be on an E39?
According to the service information, the maximum permitted current is 40 mA 16 minutes after the power is cut. A reading of a few tens of milliamps is good. Right after locking the car the consumption is higher, because the car has not yet gone to sleep.
What keeps the E39 from going to sleep and drains the battery?
The most common causes: a faulty blower resistor pack (the "hedgehog", in the front passenger footwell), which leaves the blower running, intermittent tailgate wiring, and an aftermarket alarm connected to the luggage compartment light. The rotating propeller on the climate control panel stops after about 15-16 min if the car goes to sleep.