How To Jump Start A Car With Jumper Cables

Jump starting a car with jumper cables is a skill that can rescue you from a dead battery. This guide walks you through safe preparation, correct cable connection order, and what to do if the engine does not start. You will learn how to avoid common mistakes that can damage vehicles or cause injury.

Fast Answer

Connect the red cable to the positive terminal of the dead battery, then to the positive terminal of the good battery.
Connect the black cable to the negative terminal of the good battery, then to an unpainted metal surface on the dead car, away from the battery.

Set-up ready What to have on hand

Step-by-step Guide format

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Before You Start

Park the working vehicle close to the dead one, but make sure the two cars do not touch. Turn off both engines and set the parking brakes.
Put on safety glasses and remove any loose clothing or jewelry. Check both batteries for cracks, leaks, or corrosion before you attach anything.
Locate the positive and negative terminals on each battery. They are marked with plus and minus signs, and the positive terminal is usually larger.
Untangle the jumper cables and inspect them for damaged insulation or exposed wires. If you find any damage, do not use those cables.

Check first: Batteries contain acid and can produce explosive hydrogen gas. Never lean over a battery when connecting or disconnecting cables, and never let the cable clamps touch each other. If you see smoke, sparks, or smell rotten eggs, step away and call for professional help.

Step-by-Step Instructions

Position the vehicles and turn everything off

Park the working car so its battery is within reach of the jumper cables, but keep the two vehicles at least a few inches apart. If they touch, a short circuit can occur when you connect the cables. Turn off both engines, set the parking brakes, and put automatic transmissions in park or manual transmissions in neutral. Turn off all accessories such as headlights, radio, and air conditioning in both cars. This reduces the electrical load and lowers the risk of a spark when you make the final connection. Open both hoods and secure them with the prop rods. If it is windy, position the cars so the hoods block the wind, which helps you work without the hoods falling. As a practical check, confirm that the battery terminals are clean and free of heavy corrosion. Corrosion increases resistance and can prevent the jump start from working. If you see white or blue buildup, clean it with a wire brush or a mixture of baking soda and water before proceeding.

Tip: If the dead battery has removable vent caps, check that the fluid level is above the plates. If it is low, do not attempt a jump start; the battery may be damaged internally.

Connect the red cable to the positive terminals

Take the red jumper cable and attach one clamp to the positive terminal of the dead battery. The positive terminal is marked with a plus sign and is usually larger than the negative one. Wiggle the clamp to ensure it bites into the metal and makes a solid connection. Then attach the other end of the red cable to the positive terminal of the good battery. Again, make sure the clamp is secure and not touching any other metal part. This order matters because the positive terminal is the live side, and connecting it first reduces the chance of a spark near the battery. As a practical check, tug gently on each clamp after attaching it. If a clamp slips off easily, reposition it or squeeze it tighter. A loose connection will prevent current from flowing and may cause arcing, which can damage the battery or create a fire hazard. Keep the red cable away from moving engine parts such as belts and fans.

Tip: If the positive terminal is hard to reach, use a terminal puller or a small wire brush to clean it first. Never let the red clamp touch any metal other than the positive terminal.

Connect the black cable to the good battery and a ground point

Attach one end of the black jumper cable to the negative terminal of the good battery. The negative terminal is marked with a minus sign and is usually smaller. Then, instead of connecting the other end to the negative terminal of the dead battery, attach it to a solid, unpainted metal part of the dead car's engine block or chassis. Good spots include a bolt on the engine block, a metal bracket, or a dedicated ground stud. Avoid connecting to the negative terminal of the dead battery because the battery may release hydrogen gas, and a spark at that location could cause an explosion. As a practical check, make sure the metal surface you choose is clean and free of paint, grease, or rust. If necessary, scrape a small area with a screwdriver to expose bare metal. The connection must be tight so current can flow. Keep the black cable away from the red cable and any moving parts.

Tip: If you cannot find a suitable ground point, connect the black cable to the negative terminal of the dead battery as a last resort, but do so with caution and keep your face away from the battery.

Start the working vehicle and let it run

Start the engine of the working vehicle and let it idle for a few minutes. This allows the alternator to send current through the jumper cables to the dead battery. Do not rev the engine; a steady idle is enough. While the engine runs, you may notice the dead car's interior lights or dashboard lights come on, which indicates that power is reaching the battery. As a practical check, after two or three minutes, try turning on the headlights of the dead car. If they are bright, the battery is receiving a charge. If they are dim or do not come on, the connection may be poor or the battery may be too far gone. In that case, turn off the working car and recheck all cable connections. Make sure the clamps are tight and that the ground connection is on bare metal. If everything looks good, let the working car run for another few minutes before trying to start the dead car.

Tip: If the working vehicle has a volt gauge or a battery light, watch it while the cables are connected. A significant drop in voltage may indicate a heavy load or a poor connection.

Start the dead vehicle and disconnect the cables

With the working car still running, attempt to start the dead vehicle. If it starts, let both engines run for a few minutes to stabilize the charge. Then, carefully disconnect the jumper cables in the reverse order of connection. First, remove the black cable from the ground point on the dead car. Second, remove the black cable from the negative terminal of the good battery. Third, remove the red cable from the positive terminal of the good battery. Finally, remove the red cable from the positive terminal of the dead car. As a practical check, after disconnecting, keep the revived car's engine running for at least ten to fifteen minutes. This allows the alternator to recharge the battery. If the engine dies as soon as you disconnect the cables, the battery may not be holding a charge. Turn off the engine and inspect the battery terminals for looseness or corrosion. If the problem continues, the battery or alternator may need professional attention.

Tip: Never let the cable clamps touch each other or any metal surface while disconnecting. A spark could ignite battery gases or damage the electrical system.

What to do if the car does not start

If the dead car does not start after a few attempts, turn off both engines and wait a minute. Then check that all cable connections are tight and free of corrosion. Make sure the ground connection is on bare metal, not paint or plastic. If the connections are good, try letting the working car run for five to ten minutes to build a stronger charge before attempting again. If the dead car still only clicks or does nothing, the battery may be too deeply discharged or damaged. In that case, a jump start may not be enough. As a practical check, look at the battery terminals for signs of swelling, cracks, or leaking fluid. If you see any of these, do not continue. Call a professional for help. Also, check the battery cables themselves for loose or corroded ends. A poor cable connection can mimic a dead battery. If you have a multimeter, you can check the battery voltage, but only if you are comfortable using one.

Tip: If the dead car starts but dies immediately after you disconnect the cables, the alternator may be failing. Have the charging system tested by a mechanic.

Quick Reference

Situation	Action	Why it helps
You need to connect the cables but are unsure which terminal is positive.	Look for the plus sign and the larger post on the battery. The positive cable is usually red.	Connecting the cables backward can damage both vehicles' electrical systems and cause a spark.
The dead car does not start after the first attempt.	Turn off both engines, recheck all connections, and let the working car run for five minutes before trying again.	A longer charge time can provide enough current to start the engine if the battery is not damaged.
You see sparks when making the final connection.	Stop immediately and separate the cables. Check that you are connecting to the correct terminals and that the ground point is bare metal.	Sparks can ignite hydrogen gas from the battery and cause an explosion or fire.

Common Issues

The jumper cables are too short to reach between the two cars.: Reposition the vehicles so the batteries are closer, but keep the cars from touching. If the cables still do not reach, you may need to use a longer set or call for assistance.
The battery terminals are heavily corroded, preventing a good connection.: Clean the terminals with a wire brush or a mixture of baking soda and water. Dry them thoroughly before attaching the cables. Corrosion increases resistance and can stop the jump start from working.
The dead car starts but then dies as soon as the cables are removed.: Keep the engine running and have the alternator and battery tested. The battery may not be holding a charge, or the alternator may not be charging properly. Do not rely on repeated jump starts; get the charging system checked.

Advanced Tips

If you frequently jump start cars, consider carrying a portable jump starter. It eliminates the need for a second vehicle and reduces the risk of connecting cables incorrectly.
For vehicles with sensitive electronics, use a surge protector between the jumper cables and the battery to prevent voltage spikes from damaging the computer.
When jump starting in cold weather, let the working car run longer before attempting to start the dead car. Cold reduces battery capacity and makes starting harder.

Final Checklist

Ensure both vehicles are parked close but not touching, with engines off and parking brakes set.
Check that the jumper cables are in good condition and that you know which clamp is positive and which is negative.
Connect the red cable to positive terminals first, then the black cable to negative on the good battery and a ground point on the dead car.
After starting the dead car, disconnect the cables in reverse order and keep the engine running for at least ten minutes.

FAQ

Can I jump start a car with a dead battery using another car?

Yes, you can jump start a car with a dead battery using another vehicle, provided both have standard 12-volt batteries and you follow the correct connection order. The working car's engine should be running when you attempt to start the dead car. Always connect positive to positive first, then negative to a ground point on the dead car. Never connect the negative cable to the dead battery's negative terminal unless absolutely necessary, as a spark could ignite hydrogen gas. If the dead car does not start after a few tries, the battery may be damaged or the alternator may be faulty, and you should seek professional help.

What should I do if the jumper cables get hot?

If the jumper cables become hot to the touch, disconnect them immediately. Hot cables indicate a heavy current draw or a short circuit, which can damage the cables and the vehicles. Turn off both engines and inspect the cables for damage. Check that the connections are correct and that the clamps are not touching each other or any other metal. Let the cables cool before attempting again. If the problem persists, the dead battery may have an internal short, and you should not continue jump starting. Call a professional to test the battery and charging system.

Can I jump start a car with a completely dead battery?

A completely dead battery may not accept a jump start because it cannot hold enough charge to crank the engine. If the battery is deeply discharged, you may need to let the working car run for several minutes to transfer some charge before attempting to start. However, if the battery is old or damaged, it may not recover. In that case, you will need to replace the battery or have the car towed to a service station. Always check the battery for signs of damage, such as swelling or cracks, before attempting a jump start.