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Knowing how to jump start a car is a skill that all car owners should possess. It is not a difficult thing to learn, and can save a lot of time and frustration in the case of a dead battery. The first thing to know is how to tell if a dead battery is the problem, as opposed to some other mechanical issue. If you turn the key in the ignition and the car makes a clicking noise, a sputter, or does nothing at all, you will need to use jumper cables to get the car started up again. If the headlights, radio and heater all work, or if the engine cranks, but doesn't start, the problem is not in the battery.
Read through your car's owner manual, to see if there are any special instructions for charging. The owner's manual will also probably have jumping instructions, in case you need them. It is always a good idea to keep a pair of jumper cables in your vehicle, as you can never be sure that someone stopping to help will have their own pair. They don't take up much room, and are a very wise investment. A flashlight, in case you need to jump start a car in the dark, and a hand towel are also good to have available.
To jump start a car, you will first need a second vehicle with a working battery. Put the two cars close to each other, so that the cable can reach between the batteries. Turn both cars off, and then open the trunks. Check to make sure that all of the wires are tight, which can potentially cause the battery to act like it is dead.
The jumper cables have two clamps on each end, one red and one black. Connect the red clamps to the battery first. The battery should be labeled, showing which terminal is positive and which is negative. Wiping the batteries with the towel, or some other cloth, may make it easier to read. If the terminals are not labeled, just remember that the larger terminal is almost always the positive side.
After both of the red ends have been connected, connect the black clamp to the negative terminal of the charged car only. On the side with the dead battery, the clamp should be attached to a clean, unpainted metal part on the car. The engine block is usually a good place to connect to. Connecting the black clamp to the dead battery can cause several sparks to fly out, and will not allow the battery to charge correctly. It may even lead to an explosion.
The next step to jump start a car is to turn on the charging car, and let it run for two or three minutes. This will send energy over to the dead battery, allowing it to gain enough juice to start. Start up the car that had the dead battery. If it starts without a problem, then remove the cables in the reverse order of how they were connected, taking the black cables off first. Let the vehicle run for 30 minutes, while either driving or idling, to fully charge the battery.
If the car does not start, check to make sure that the cables are all securely attached, and then try again. If the vehicle still won't start, the battery may need to be replaced, or there may be something else wrong with the vehicle. These instructions may not work for all makes and models; check with your owner's manual or with a mechanic before you attempt to jump start a car.