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How to jump start your car

As the first chilly days of autumn arrive, some drivers are surprised to find that their car battery seems weak. What should they do? Pushing the car is, in any case, taboo for vehicles with catalysts. And anyway, it only helps if there's still enough voltage in the battery for the spark plugs. Pushing vehicles is usually tiresome and futile, particularly with diesels, whose engines need sufficiently high air temperatures for the first ignition sequence (prewarming). The only remaining option is jump leads, which every driver should carry in the car. But you need to be careful with them or you can cause damage.

The instruction manual for any car should usually explain how to use jump leads. The sequence in which you proceed is important. You need two things to get your car going - another car and one jump lead each for the positive and negative terminals. Connecting a fully-functional battery to a flat one is the simplest solution if a car won't start.

Step by step


Only use batteries with the same rated voltage.


Switch off both engines and all electrics (except the donor vehicle's hazard warning lights).


First connect the red jump lead to the positive terminal of the flat battery, and then attach the clip on the other end of the lead to the donor battery.


Then connect the black cable to the negative terminal on the donor vehicle before attaching the free end of the cable to a metal part away from the battery on the vehicle with the flat battery. The best area may be the engine block (see vehicle manufacturer's instructions).


Make certain that the cables do not come into the range of the exhaust or the drive belt.


Start the engine of the donor vehicle, and then start the engine of the vehicle with a flat battery (max. 15 seconds) and let it run.


Remove the cables in the reverse order.

Once you have got it started, drive the vehicle that had a flat battery for a lengthy distance to charge up the battery or else recharge it at the nearest charger. NB: The bodywork of the two vehicles must not touch while jump leads are being used.

Rely on Bosch

If you ever have any problems, or need help or advice, we have a nationwide network of approved garages whose technicians have been trained to very high standards. These Bosch service agents are independently owned businesses and are committed to providing high standards of work to their customers.

You can use our Dealer Locator facility to find a Bosch Car Service workshop near you.

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Jump start diagram

How to jump start your car

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