This is a video about how to tell if the car is positive or negative ground. This video explains step by step how to detect the positive or negative ground. To know the ground of the car is very important to determine where the application is wired. To detect the ground of the car is easy, it use the battery with the both negative terminal and positive terminal is connected with cable. Then the negative cable is connected to the frame of the car. This is a negative ground car. Here is the video:

Beside that, the dual six volts batteries are used. These batteries is connected together leaving the one is positive terminal and one is negative terminal. In this set up, the positive cable goes to the ground. This batteries is being used in positive ground car. The larger terminal is always positive.