Connected jumper cables in the wrong order

Symptoms

• Sparks appeared when connecting cables
• Cables were connected but the car still won't start
• Not sure if positive and negative were matched correctly
• A fuse blew or a warning light appeared after jump-starting

Likely causes

• CommonPositive and negative reversedReversing polarity can blow fuses, damage the alternator diodes, or damage sensitive electronics.
• PossibleNegative cable connected to the dead battery instead of grounded metalThis is a common mistake that increases the risk of sparking near battery gases.
• CommonCables connected in the wrong order (not necessarily wrong polarity)The standard safe order matters even when polarity is correct.

What to do

1. Stop and disconnect all cables in reverse order if you're unsure the connections were correct.
2. Confirm which post is positive (+) and negative (-) on both batteries; posts are usually marked and the positive is often the larger post.
3. Reconnect properly: red-to-positive on the dead battery, red-to-positive on the good battery, black-to-negative on the good battery, then black to an unpainted metal surface on the dead car's engine (not its battery).
4. Double check every clamp is firmly attached to bare metal or the correct post before starting either engine.
5. If you suspect polarity was reversed and something sparked or a fuse blew, do not try again; check for a blown fuse in the fuse box before attempting another start.
6. If everything looks correct and the connections are solid, try starting the working car first, let it run a couple minutes, then try the dead one.

Tools and parts

• Jumper cables or a jump starter pack

When to call a pro

If a fuse blew, a warning light appeared, or electronics stopped working after a bad jump, have the electrical system checked before assuming it's fine.

Safety