Originally Posted by 05CrewDually
The current flows from the negative side. This is why older Brit cars were positive earth.
The reason you should ALWAYS disconnect the negative terminal FIRST, is so if you slip with the wrench and touch the vehicles sheet metal or chassis you don't short out and cause a shower of sparks and damage to your wrench!
Disconnecting negative first has nothing to do with the direction of flow of the current. If you were on an old Brit car, you'd want to disconnect the positive first.
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