When jump starting a vehicle, where should the last connection be made?

When jump starting a vehicle, making the last connection to the engine block of the dead vehicle is important for safety and effectiveness. This method minimizes the risk of sparks near the dead battery, which could ignite any hydrogen gas that may be present—a common hazard with batteries.

By connecting to the engine block rather than directly to the negative post of the dead battery, you create a safer ground connection away from the battery. The engine block acts as a common ground point and facilitates the flow of current from the good battery to the dead battery, enabling the dead vehicle to start without risking an explosion or fire.

In comparison, connecting to the positive post of the dead battery could lead to potential arcing or sparking near the battery terminals. Similarly, connecting to the alternator of the good vehicle or the negative post of the good battery introduces unnecessary risks. Thus, connecting to the engine block effectively reduces these hazards while still allowing the dead battery to receive the necessary charge.