Check the headlights. Are they dim or bright? (Note that in some cars you will need to turn the ignition on to test the headlights). If they are dim, it’s likely your battery is the culprit. If your headlights are bright, you do not have a dead battery and a jump start will not help. Ensure that the doors will unlock when you push the button on the key and/or try to open the door from the outside, the interior lights work, and the clock or GPS (if equipped) moves or powers on. Put the key in the ignition and see whether your dashboard lights up as usual. Test the stereo. In most cases, even with a low battery you should see some dashboard lights and get some sound out of the stereo. If you do not get a flicker out of your dashboard, you may have a problem with your ignition switch. Try to start the car. Does it turn over very slowly, or does it crank quickly? If it cranks quickly, you do not have a dead battery and a jump start will not help. If it cranks slowly, or not at all, you probably have a dead battery.
The positive terminal will be marked with a plus sign (+) and will usually have a red cable attached on it. The negative terminal will be marked with a minus sign (-) and will usually have a black cable attached to it.
If the cars are touching, jumping the battery can cause a dangerous electrical arc between the vehicles.
Check that the battery cables are firmly connected to the battery posts. Loose cables can prevent a vehicle from starting yet allow the radio and lights to appear normal. Use a proper sized wrench to tighten the cable terminal to the battery post. Avoid touching any other part of the vehicle with the wrench when it is on the terminal as a large spark and explosion can occur. If you are unable to tighten the terminal enough to prevent it from moving, in an emergency, you can use a metal shim made from a soda or tin can. Place the shim between the battery post and the cable terminal to allow it to be sufficiently tightened to prevent the terminal from moving on the battery post. Replace the battery cable/terminal as soon as possible. This is not a long term fix. It may be necessary to remove the disabled automobile’s battery cables from the battery terminals and clean both cables and terminals. Corrosion between the battery and cable terminals can prevent a vehicle from starting. Use a stiff wire brush to remove all corrosion. Reconnect the cables to the battery terminals and jump the car. Remove any positive (+) red post protective covers if applicable.
Connect one red clamp to the positive (+) terminal of the dead battery. Connect the other red clamp to the positive (+) terminal of the good battery. Connect one black clamp to the negative (-) terminal of the good battery. Connect the other black clamp to a piece of grounded metal on the dead car, preferably the bolt where the thick negative cable from the battery connects to the chassis. If this is not practical, look for shiny metal (not painted or oily) that is attached to the engine. Usually a nut, bolt or other protruding shiny metal will work. You may see a small spark when you connect to a good ground. As a last resort, you may connect to the negative (-) post of the dead battery, but this risks igniting hydrogen gas coming off the battery. Some cars have the battery hidden under additional electronics, in which case you will need to look for the terminals labeled “-” and “+”. Make sure none of the cables are dangling into the engine compartment, where they could be exposed to moving parts.
Disconnect the black clamp from grounded metal on the dead car. Disconnect the black clamp from the negative (-) terminal of the good battery. Disconnect the red clamp from the positive (+) terminal of the good battery. Disconnect the red clamp from the positive (+) terminal of the dead battery. Replace any positive (+) red post protective covers if applicable. These covers help prevent accidental short circuiting the battery.
