When isolating the electrical system of a vehicle, which terminal should be removed first to minimize arcing?

• A. Positive terminal first
• B. Negative terminal first
• C. Remove both at once
• D. Do not disconnect the battery

Answer: (B)

When isolating a vehicle’s electrical system, break the circuit from the ground side first. Disconnecting the negative terminal reduces the chance of arcing because the vehicle’s frame is tied to that negative post, so removing it opens the circuit with respect to ground. This means a tool touching the positive post and the car’s metal won’t have a live path back to the battery, minimizing sparks. If you remove the positive terminal first, a metal tool could bridge the positive post to the chassis and create a short, causing a spark. Removing both at once isn’t practical and doesn’t eliminate the risk as effectively. Not disconnecting the battery leaves the system connected and arcing risk remains.