Do You Remove Positive Or Negative Battery Terminal First. The heat can cause battery parts to melt and the hydrogen gas can cause a crack in the battery. If you begin to remove the positive side before the negative and your wrench would make contact with any part of the vehicle then you could cause a short in the system.
The reason they say to disconnect the negative and not the positive is because while taking the positive connection off with a wrench if you happen to touch anything with the wrench while its on the positive terminal it can arc and be dangerous. The positive terminal should be connected first when installing a new car battery to a car. If positive terminal is removed first then chances of a spark are more if this terminal touches the body through the metal spanner or wrench you are opening with is grounded accidentally and may end in flames because lot.
Clean any corrosion off of the battery and terminals with a can of spray-on battery cleaner.
This can cause significant sparking and damage to. Disconnecting either cable works. If positive terminal is removed first then chances of a spark are more if this terminal touches the body through the metal spanner or wrench you are opening with is grounded accidentally and may end in flames because lot. However if the negative was already connected to the battery and I shorted the positive to the body with the spanner there would now be a short circuit with a big spark and a possible fire.
