How to jump start a car

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Woman with jumper cables
When you jump start a car, you'll want to connect the red wire to the positive terminal and the black wire to the negative terminal
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Jump-starting a car typically requires jumper cables and a working car battery.

Let me start off by saying that this article is about how to jump start a car or pickup truck with real jumper cables that are used under the hood of a car. The tiny little wires that plug into each vehicle's power sockets (formerly known as cigarette lighters) are not a good choice and should be used only as a last resort. The higher quality your jumper cables are, the easier (and safer) it will be to get the car running.


Getting Started


Before attempting to jump start a car or truck, there are some things you need to know. First off it's very important that you never try to jump start a battery that has a crack in it. This could potentially cause the battery to explode and spray you with battery acid. Hopefully it goes without saying that this would be a bad thing.If there is a crack in the battery, it won't even hold a charge for long and will always be a hazard. So just go ahead and buy a new one, if yours has a crack.


Connecting the Cables


You must also identify which post (terminal) on your battery is positive and which is negative. Typically the positive terminal will be connected to a red wire and the negative will be connected to a black wire. However, there is always some possibility in older cars that someone, somewhere along the lines has used the wrong wire, so the best way to check is on the battery itself. With every battery there will always be a plus (+) sign near the positive terminal and a minus (-) sign near the negative terminal.

If there's so much muck built up on top of the battery that you can't see the symbols, you'll need to clean the top of the battery well enough to find the + and - symbols. Do not do this with your bare hands! Find a towel or washcloth or at least paper towels to do this.


Note that if any liquid from the battery gets on your hands during any part of this process, be sure to wash them immediately.


Checking Your Car


Now, before you get going you'll need to make sure that everything in your power sockets is unplugged. Also, make sure everything in your car that draws electricity is turned off. This includes the radio, headlights, windshield wipers and window defogger.


There are two reasons to do these things. First, it will be easier for the other car to transfer the necessary voltage to get the car started if all of these things are not drawing electricity at the same time. The second is that jump starting your car can cause a pretty hefty electrical surge with the potential to damage any electrical items plugged in or powered on at the time.


Lining Up the Vehicles


Get the vehicles positioned so that the two batteries are as close together as possible, while still leaving enough room for you to move in between the cars and get the hoods up. Pay attention to where the battery is in the engine compartment of each vehicle. Sometimes it's on the driver's side and sometimes it's on the passenger's side. If the two batteries are on the same side, you'll probably need to get the cars nose to nose. If they're on opposite sides, there's a good chance you'll be able to do this with the cars parked side-by-side.


Connecting the Cars


Once you have the second vehicle lined up correctly, turn the engine off so that neither car is running. Now you're ready to actually connect the battery cables. Be sure to do this in the correct order to avoid shocking the mess out of yourself, accidentally starting a fire with sparking wires or potentially causing a battery to explode. Also be absolutely sure that you never allow any cable ends to touch each other or any part of the car while connecting or disconnecting them.


1. Connect one end of the positive cable (this should have a red handle) to the positive terminal (+) of the dead battery.


2. Connect the other end of the positive cable (the other red handle) to the positive terminal (+) of the good battery in the other vehicle.


3. Connect one end of the negative cable (this should have a black handle) to the negative terminal (-) of the good battery.


4. Finally, connect the other end of the negative cable to a metal part of the dead car's engine compartment that has no paint. Usually there are some large bolts or stabilizer bars inside the engine compartment that can be used for this. Painted parts will not work for this; it must be bare metal. As a last resort if you cannot find any unpainted metal parts in the engine compartment, you can attach the cable to the negative terminal itself. It's probably safer to find a piece of metal away from the battery if possible.


When you make that last connection, it's normal to see a spark. This is not a bad thing. It means the proper connections have been made. However, it should only be for a moment. This spark is why it's safer to connect to a metal part of the engine compartment rather than the battery itself.


Start the engine of the second car (the one that starts). It needs to run for a few minutes with the cables connected. This cranks up the alternator and sends extra juice to the batteries. There is some evidence that jump starting a car can occasionally damage the second car's alternator, so some people advocate turning off the good car and removing the cables at this point before attempting to start the dead vehicle. However, this reduces the chances of getting the car started so it's up to you.


At this point, make sure that the doors of the dead car are closed. Even the lamp on the ceiling of the car will drain the battery, so all doors need to be closed so no lights are on in the vehicle. If you're in a fuel-injected car (which is pretty much any vehicle made after 1990 or so), don't pump the gas pedal while you're trying to get it started.


Now crank the engine. Assuming there were no other problems with your vehicle, it should start up easily.

Removing the Cables


When you're ready to remove the cables, do it in exactly the opposite order as you attached them.


  • Remove the negative cable clamp from the formerly dead car.


  • Remove the negative cable clamp from the second car.


  • Remove the positive cable clamp from the second car.


  • Remove the positive cable clamp from the formerly dead car.

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