How to Jump-Start a Car

Things you’ll need

  • Jumper cables
  • Rag
  • Flashlight
  • Booster car


  1. Remember, connect only batteries of similar voltage! 12 volt to 12 volt, 6 volt to 6 volt. Check owner’s manual (or examine the battery) to determine voltage.
  2. Get the good and the ���dead��� batteries as close together as possible by maneuvering the working car. But do not allow the bumpers to touch!
  3. Safety precaution: Cover vent openings of both the good and ���dead��� batteries with rags to prevent possible battery-acid splatter.
  4. Place both cars in Park position with emergency brakes on. Unravel the jumper cables, making sure that the clamps on either end never touch each other.
  5. (1) Connect one red-end clamp to the positive ( + ) battery post of the ���dead��� battery. NOTE: Batteries are designed differently; some have the posts on top; some have them on the side. All posts have markings on or next to the post indicating positive ( +) or negative (-).
  6. (2) Connect the other red-clamp to the positive ( + ) post of the good battery.
  7. (3) Connect one black-end clamp to the negative (-) post of the good battery.
  8. (4) Carefully connect the other black-end clamp to some large metallic part of your car’s engine block (see illustration). Never connect it to the negative (-) post of your car. This prevents sparking close to the battery, which could ignite battery gases. Take special care to keep the jumper cables away from the fen belt or other moving parts of the engine.
  9. Now, you’re ready to jump-start your car. Start the working car and run it at idling speed. Then start your car.
  10. Once your car has started and is running, immediately disconnect the jumper cables in this order: (4) black-end clamp on your car’s engine block, (3) black-end clamp on good car, (2) red-end clamp on good car, (1) red-end clamp on your car.


  • Always check your owners manual before jump-starting a car. Some new cars have special ‘jump-start lugs’ where jumper cables are attached rather than to the battery cables. These allow the potentially damaging surge of current to bypass the electrical system (and all those fancy, new onboard computers).
  • If the dead car won’t respond, there might be a problem in another part of the ignition system. Consult a mechanic.
  • After you jump-start a dead car, run the engine for half an hour to charge the battery.


  • Avoid starting or running the charged car while jump-starting the dead one. This is a common mistake in jump-starting cars. This can release a power surge into the charging car and blow a fuse, damage the alternator, or harm other areas of the electrical system.
  • Many early British cars, such as Jaguars and MGs, use a positive ground instead of the popular negative ground. Consult a mechanic if you’re in doubt about how to jump-start your particular car.
  • The voltage from a car battery is dangerous whether the engine is running or not. Do not touch the metal ends of the jumper cables with your hands, nor touch them to each other. Never grasp both battery terminals at the same time.



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