How to Jump Start a Car

It’s easy to jump start your car if you have a dead battery. Batteries go dead for all sorts of reasons, but usually it’s our fault (left a light on for example). This is a good thing, because that means a simple jump-start will get you back on the road with no permanent damage.

What You’ll Need to Jump Your Car

  • Another car, running
  • Jumper cables
  • Safety glasses

You’ll need to park the running car next to the dead car that needs the jump in such a way that the jumper cables can reach both batteries. If you aren’t sure where the batteries are under each hood, take a peek before you park next to the dead vehicle. Important: Never drive with your hood raised. Not only do you have no visibility, you could damage your hood components or the hood itself.

Don’t be nervous about your battery connections, but also know that it’s very important that you do not mix up the cables or you can do serious damage! With both cars parked next to each other, turn both keys to the OFF position. Not only will this protect your car’s electrical system from any surges, it’s always safer under the hood with the engine off.

Cable Connection Steps

  1. Be sure both ignition switches are in the OFF position.
  2. Locate the “+” (positive) and “-” (negative) sides of each battery. They should be clearly marked on the battery itself. On most cars the positive (+) side often has a red cover over the battery post and wires. NEVER assume a red color cap or battery cable automatically means the battery terminal is the positive terminal. Always verify the battery has a “+” sign near the terminal.
  3. Attach the red cable to the “+” side of the dead battery.
  4. Attach the other end of the red cable to the “+” side of the live or good battery.
  5. Attach the black cable to the “-” side of the live or good battery.
  6. Attach the other end of the black cable to a section of unpainted metal on the vehicle with the dead battery. This can be as small as the head of a bolt, as long as the jumper cable will reach.
Photo of Properly Connected Jumper Cables to Jump
Properly Connected Jumper Cable Diagram

Note the pale blue corrosion under the red protective cover in the photo above. Corrosion creates poor connections; this is why we recommend servicing battery terminals.

Important Tips

  1. Attach the jumper cable to the most secure attachment point you can find on the car’s permanent battery cables.
  2. You might be tempted to attach the last negative jumper cable to the “-” side of the good battery, but this isn’t recommended. Batteries often leak small amounts of Hydrochloric acid, which could turn into flammable gas around the battery. This gas (and battery) could explode if the cable creates a spark near the battery. This is why we recommend hook the negative jumper cable to a bolt or unpainted metal AWAY FROM THE BATTERY.
  3. We also do not recommend wiggling the cable clamps to get a good connection when they are all hooked up because this could create a spark and a possible explosion.

Now that you’re all set up, it’s time to turn some keys. First, start the car with the good battery, and leave it running. If the battery in the dead was really badly drained, it may help to leave them connected for several minutes with the good car running before you try to start the dead car. This will allow a little charge to build up in the dead battery.

Turn the key in the dead car to start and it should fire right up! As long as you don’t have any issues with the alternator in the dead car, you can disconnect the jumper cables right away.

Disconnecting the Jumper Cables

Disconnecting the jumper cables should happen in the reverse of connecting them.

Disconnect the black (negative) cables first, then disconnect the red. Remember, the red (positive) cables are the ones that can cause a short if they touch the car while they are connected to the battery.

If the dead car doesn’t turn over, or turns over very slowly, or does not start, It will be time to call a tow truck and have the vehicle towed to a reputable repair and service facility.

How to jump start a vehicle Synopsis

  1. Identify battery locations and the positive (+) and negative (-) battery terminals on both batteries. *WARNING, do not mix up the jumper cables when attaching them, severe damage will occur to both vehicles electrical systems
  2. Make sure both ignition switches are turned off on both cars
  3. Attach positive (+) jumper cables to both battery’s positive terminals
  4. Attach one negative (-) jumper cable to the dead battery’s negative terminal
  5. Attach the remaining negative (-) jumper cable to bare metal like a bolt or engine bracket away from the battery
  6. Start the good vehicle and let it run for several minutes to help charge the dead battery
  7. Start the vehicle with the bad battery. Once it starts and runs, disconnect the battery cables in reverse order
  8. Let the vehicle with the dead battery run for at least 20 minutes to charge the dead battery

Remember, safety first. If you are unsure – call someone!

Towing Company: A1 Towing, 406-443-4044
Service and Repair Shop: J4 Automotive, 406-227-8622

Important note: This content is created to help you become more familiar with your vehicle. The information presented herein is generic in nature and applies to almost every vehicle on the road today. For specific information and recommendations for your particular vehicle, we recommend referring to your vehicle’s owner’s manual. If you do not have one, we recommend purchasing one for your vehicle. The owner’s manual will list the proper operating procedures, maintenance intervals and requirements and the fluid types needed to keep your vehicle in a reliable and trouble free state of operation. This in turn will deliver the best return on your investment and provide you with the optimum safety and economy in operation.