Avoid a jump start that could cost thousands
Car electronics are becoming increasingly sensitive to voltage spikes usually caused by jump starts. Most vulnerable to these spikes are the Anti-lock and air bag control units, which cost upwards of $1,000. The best prevention is to have your charging system and battery tested regularly. However, in the event a jump start is necessary, great care must be taken to avoid damage to the electronic control system. To safely jump start your vehicle there is a six-step process to follow, with the fifth step the most commonly overlooked, and very important.
Please note that jump starting equipment found on some tow trucks operate at 18 and up to 24 volts! Damage to certain electrical components is assured if this equipment is used. Disconnecting the battery leads and charging the battery is recommended. However, in certain circumstances, jump starting may not be avoidable.
To protect the electric components in the car, follow the procedure described below.
1. Ensure that the vehicle being jump started and the vehicle used to jump start are not touching.
2. Ensure that both vehicles have batteries of the same voltage and of approximately the same ampere-hour rating (ampere-hour rating must be similar to ensure sufficient power for jump starting).
3. Carefully observing polarity, connect the positive jumper cable to the B+ Junction Post (or battery positive terminal, if vehicle is not equipped with B+ Junction Post) of the vehicle to be jump started, and then to the battery positive terminal of the vehicle being used to jump start.
4. Next connect the negative jumper cable to a CHASSIS GROUND (e.g., bolt at front shock absorber upper mount) on both vehicles. In this manner, sensitive electronic components will be afforded more protection from voltage surges by the damping action of the chassis ground.
5. Jump start the vehicle. Before disconnecting the jumper cables, switch on:
- Heater fan to highest speed
- Rear window defroster
- Low beam headlights
By switching on these power consumers, voltage surge at the moment of jumper cable disconnection is minimized.
6. Disconnect the negative jumper cable, then disconnect the positive cable. Disconnecting the cables in this order ensures that any momentary arcing that might occur is away from the battery (in the case of vehicles with the battery in the engine compartment) and any gases produced by the battery.
Some text is courtesy of BMWNA.
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