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Do you attach red or black first?

When it comes to jump starting a car with jumper cables, a common question that arises is whether you should attach the red cable or the black cable first. There are differing opinions on this, but most experts agree that it does not actually matter which one you attach first as long as you follow the proper overall procedure.

What is Jump Starting?

Jump starting a car refers to using an external power source, usually another vehicle’s battery, to provide enough power to start the engine of a vehicle with a dead or weak battery. This is achieved by connecting the two vehicles’ batteries together using jumper cables, also known as booster cables or jump leads.

The basic procedure involves connecting one end of the red jumper cable to the positive terminal of the dead battery, and the other end to the positive terminal of the live battery. The black cable is then connected from the negative terminal of the live battery to a ground on the dead vehicle, away from the battery. This allows power to flow from the live battery to the dead battery in order to turn over the starter and get the engine running.

Does Connect Order Matter?

When it comes to whether you should attach the red or black jumper cable first, there are a few schools of thought:

  • Attach red first – This approach says you should always connect the red positive (+) cable first, before attaching the black negative (-) cable. Proponents argue it prevents sparks or explosions from accidental shorts.
  • Attach black first – This method suggests connecting the black negative cable first, before the red positive cable. Supporters argue that attaching the negative first grounds the dead car, preventing sparks.
  • Doesn’t matter – Many experts claim the order is irrelevant as long as the final connections are red to positive and black to negative. The batteries will equalize themselves regardless of which is connected first.

So which is the proper way? The truth is that electrically, it does not matter. The effect will be the same once everything is connected properly. However, there are some factors that can influence best practices:

Reasons to Attach Red First

There are some reasons why connecting the red positive jumper cable first can be beneficial:

  • Avoids sparks – If the dead battery is completely drained, attaching the negative first can cause sparks when you go to attach the positive. Attaching red first avoids this.
  • Prevents shortage – Accidentally touching the positive and negative cables together could short the good battery if the negative is attached first.
  • Establishes initial connection – Having the initial connection be positive allows current to flow in the proper direction immediately.

For these reasons, many auto experts recommend attaching the red positive jumper cable first when jump starting a car. The initial positive connection avoids any sparks, shorts, or reverse polarity situations.

Reasons to Attach Black First

On the other hand, there are also some advantages to attaching the black negative jumper cable first:

  • Grounds dead car – Attaching black first grounds the dead car, which reduces the risk of sparks when attaching the positive cable.
  • Lets voltage equalize – Allowing the negative cable to equalize voltage differences first prevents sparks during positive connection.
  • Avoids driving up voltage – If the good car’s voltage is significantly higher than the dead car’s, attaching positive first can drive up voltage to dangerous levels.

Based on these factors, many mechanics recommend attaching the negative jumper cable first as a safer approach. Letting the cars equalize voltage minimizes sparks and electrical risk.

General Jump Starting Procedure

While the order of cable attachment can go either way, the overall procedure for jump starting a car remains the same. Here are the basic steps:

  1. Position the cars close enough for cables to reach, but do not allow them to touch.
  2. Turn off both vehicles and set parking brakes.
  3. Connect one clamp of the red jumper cable to the positive (+) terminal of the dead battery. Connect the other red clamp to the positive terminal of the good battery.
  4. Connect one clamp of the black jumper cable to the negative (-) terminal of the good battery. Connect the other black clamp to a grounded metal part on the dead car, away from the battery.
  5. Start the car with the good battery and let it run for a few minutes.
  6. Attempt to start the car with the dead battery. If it does not start within a few seconds, stop cranking.
  7. Let the good car run for 5 minutes more while connected, then disconnect cables in the reverse order – black first, then red.

The most important thing is ensuring the final connections are positive to positive, and negative to a solid ground. Do not attach the negative clamp directly to the negative post of the dead battery, as it can cause sparks. Follow these steps carefully while making the initial cable connections gently. Things like engine layout may dictate which cable you connect first for ease.

Safety Tips

When jump starting a vehicle, keep these additional safety tips in mind:

  • Check battery terminals and clean if necessary – Remove corrosion and ensure clamps make good contact.
  • Never jump start a frozen battery – Let it thaw first or it could rupture and explode.
  • Avoid moving parts – Keep hands and cables clear of any pulleys, belts, or fans.
  • Do not allow cable clamps to touch – Prevent sparks and shorts.
  • Remove jewelry and watches – Metal items can conduct electricity.
  • Work in a well-ventilated area – Batteries release explosive hydrogen gas.
  • Use proper gauge cables – Thicker cables handle battery current better.

Exercising caution and following manufacturer recommendations for your vehicle’s battery and jumper cables will help ensure a safe and successful jump start.

When to Call a Professional

While jump starting a dead battery yourself can save time and money, there are instances where it is best left to professionals:

  • You lack experience or confidence performing the procedure
  • The battery is more than 3 years old and may need replacement
  • The battery does not hold a charge even after successful jump starts
  • There are abnormal noises, smells, or leaks coming from the battery
  • Corrosion or damage make cables unable to connect properly
  • You do not have proper gauge jumper cables suited to your vehicle

Car service technicians have commercial equipment and experience addressing common battery problems that the average driver lacks. Do not take risks attempting to jump start a severely damaged or dangerous battery situation. Calling a professional tow truck or auto service can save you from being stranded or injured.


In summary, the order of connecting red or black jumper cables first is not critical. What matters is that the final connections are positive to positive, and negative to a proper ground. There are logical reasons to attach either first based on preventing sparks, allowing voltage to equalize, or enabling current flow in the proper direction.

The best practice is to follow manufacturer recommendations for jump starting sequence and cable gauge specific to your vehicle. Adhere to general safety precautions, and do not be afraid to call a professional when dealing with a severely damaged or hazardous battery. Paying attention to condition and cleaning terminals can go a long way towards successful jump starts. Knowing the proper procedures and cable attachment order will keep you prepared whether you find yourself jump starting your own or someone else’s car.