If you’ve left your headlights on at the mall or the dome light on overnight, you may get the dreaded “click” when it’s time to go. You can count on it happening at one time or another, unless you’re one of the rare people who actually notice the myriad warning bells and tones your car makes, and know which one is saying “Hey, you left the lights on!”
Jumper cables are the automotive equivalent of a defibrillator. They allow a donor vehicle to share its spark of life with yours. While you don’t have to holler “Clear!” when you use them, you’d better know what you’re doing if you want to revive the patient.
Things You'll Need
- Jumper cables
- Running vehicle
Unravel the jumper cables so that they are straight. Note that each end has two clamps: a red clamp and a black clamp.
Park the vehicle with the fully charged battery next to the vehicle with the dead battery, either facing each other or side by side. It is important that the two batteries are close enough so that the jumper cables can reach, but the cars must not touch each other. Turn off the ignition and all lights and accessories on both vehicles – leave the flashers on if needed for safety. Unplug all electronic devices, such as cell phones, MP3 players, GPS units, etc. These could be damaged by the jump start. Raise both hoods so the engines are exposed.
Attach one of the jumper cable red clamps to the positive terminal of the dead battery. A "+" sign will indicate which terminal is positive. The positive terminal is also a little bit larger than the negative terminal. You may need to remove a plastic cover on the terminal to attach the red clamp. Attach the clamp to the metal part of the terminal, and make sure the metal clamp touches nothing on the car but the battery terminal. Wiggle the clamp a bit to establish a good connection.
Attach the other red clamp in the same fashion to the positive terminal of the fully charged battery. Route the cables so they won't be near moving parts -- like the engine pulleys or cooling fan -- when you start the engines. Remember that electric cooling fans can turn on unexpectedly -- even with the engine turned off.
Locate the black clamp next to the red one you just attached to the fully charged battery. Attach this black clamp to the negative terminal of the fully charged battery.
Attach the other black clamp to the engine block of the car with the dead battery. Don't attach it to the battery. The object here is to avoid sparks near the battery, which could cause an explosion, so find an unpainted bolt or engine bracket as far from the battery as possible without getting the cable near any moving parts. Don't panic if your jumper cables spark a little bit when you make this connection.
Start the vehicle with the good battery. Let it idle for a couple of minutes to energize the dead battery. Attempt to start the engine with the dead battery. If it turns over slowly or not at all, wiggle the jumper clamp connections and try again. You may have to let the battery charge for five to 10 minutes if it was completely drained. Be patient. When it starts, let it run for a couple of minutes.
Disconnect the jumper cables in the exact reverse order: Remove the black clamp on your engine block first, followed by the black clamp on the charged battery and then the red clamp next to it. Finally, remove the red clamp on your battery. Be careful not to let a loose clamp or cable fall into moving parts, and keep the red and black clamps separated during this process.
Tips & Warnings
- Drive your vehicle around for 20 to 30 minutes after using jumper cables so your battery has a chance to charge. If you don't, you might need to use the jumper cables again the next time you want to start your car.
- Be mindful of where you turn the car off again for the first time. If the problem is with the charging system, it probably will need another jump regardless of how far you drove it.
- Some cars --- like BMWs -- have their batteries in the trunk or elsewhere. For these cars, look for a red plastic cap covering a jump connection. It should be labeled as such.
- Be very mindful of traffic around you. With the hoods up, and you between the cars, you will be invisible to oncoming traffic.