Jump Starting Your BMW
Jump-starting BMW vehicles should
be avoided, as it may cause damage to certain electrical components. The
electrical components found in BMWs (and most other cars) are designed to
handle up to 15 volts for brief periods only. Jump-starting equipment found on
some tow trucks operates at 18 volts or as high as 24 volts. Disconnecting the
battery, then charging it, is the recommended alternative.
When jump-starting is the only option, you can take these steps to ensure the
vehicle's electrical components are not damaged:
- Ensure that the
vehicle being jump-started and the vehicle used to jump-start are not
touching each other. Ground points exist on some bumpers.
- Ensure that both
vehicles have batteries of the same voltage and of approximately the same
ampere-hour rating (to guarantee you'll have enough power to jump start
the dead car).
- Connect the positive
jumper cable to the positive (B+ junction) post on the dead battery, and
then to the positive terminal on the vehicle providing the jump-start.
- Connect the negative
jumper cable to a chassis ground on both vehicles. This protects
sensitive electronic components from damaging voltage surges by using the
damping action of the chassis ground.
- Jump-start the
vehicle. Before disconnecting the jumper cables, switch on: the heater
fan at highest speed, the rear window defroster and the low beam
headlights. Activating these reduces the voltage surge at the moment the
jumper cables are disconnected.
- Disconnect the
negative cable, then the positive. Maintaining this order ensure that any
momentary arcing that might occur is away from the battery and the engine
compartment, where flammable gases may develop.
Remember, failure to follow these procedures may result in
damage to sensitive electrical components. Damage is a virtual certainty if
performed with equipment that delivers over 15 volts.