When removing a battery from a diesel engine, which terminal should you disconnect first?

When removing a battery from a diesel engine, it is important to disconnect the negative terminal first. This is because disconnecting the negative terminal reduces the risk of short-circuiting the battery. The negative terminal is typically connected to the vehicle's chassis or ground. By removing this first, you prevent any potential electrical shorts that could occur if a tool accidentally contacts a positive terminal while you're working on the battery.

Once the negative terminal is disconnected, it is safe to disconnect the positive terminal without the risk of creating a circuit between the positive terminal and any grounded part of the vehicle. Properly following this sequence helps ensure safety, preventing sparks or damage to the electrical system of the engine. This practice is standard safety protocol for working with batteries in automotive and machinery applications.