Splice
The physical body of your DC Equipment is always your GROUND. This GROUND is where you also connect your -VE.
Normally they are used as if they were same but ground means that this connection is linked to earth, negative means that this connection is linked to a negative terminal. It is possible that someone has named the terminal incorrectly and named it ground instead of negative. Voltage between negative terminal and ground is normally 0, that means that they are on the same potential and that there is no danger of short-circuit.
In many cases, a ground symbol is used to save drawing extra lines in a diagram and/or to show that a metal cabinet is used as a return path to save wiring in the ground side.
If one terminal of a battery is connected to the frame of the equipment in which it's used, the connection is generally made with the ground, and this is called a ground connection. It refers to the reference point from which all other electrical voltages are measured.
Static electricity may build up and discharge through the circuits you are working on. This may damage them. Removing the ground cable, removes the discharge path to ground.
Radar communication is electronic communication without the use of wires. Radar communication can be between a ground terminal, like a cell tower, and a satellite. Or it can be between ground towers and also between two or more satellites.
Batteries are neither positive nor negative ground. It is the circuit itself that determines the common ground. For example: If I have two circuits, one needing 6vdc negative ground and the other needing 6vdc positive ground, the battery would be installed the same way in both circuits (positive terminal on the battery to the positive connection in the circuit, regardless of whether the circuit is positive or negative ground). The reason for labeling the ground as Positive or Negative has more to do with how the circuit is wired up, than the actual voltage source. The explanation for that is beyond the scope of this answer.
To wire a toggle switch to your wiper motor, first, identify the motor's power and ground terminals. Connect one terminal of the toggle switch to the power supply and the other terminal to the wiper motor's power terminal. Then, connect the ground terminal of the motor to the vehicle's chassis or a suitable ground point. Ensure all connections are secure and insulated to prevent short circuits.
checkA loose connection on the battery posts, starter battery terminal or line to fuses and relay circuits, battery ground cable connection or a bad connector strap from the engine to the frame. How do you get it cranked in the first place?
To wire a 12-volt positive ground coil, first ensure the ignition switch is off. Connect the positive terminal of the coil to the positive battery terminal, and then connect the negative terminal of the coil to the ignition switch or distributor. Finally, connect the other side of the ignition switch to ground. Make sure all connections are secure and insulated to prevent short circuits.
bad ground or bad terminal connection!
To connect a twin hooter with a relay, first ensure the vehicle's electrical system is off. Connect the positive terminal of the battery to one terminal of the relay (usually the 30 terminal). Connect the other terminal of the relay (terminal 87) to the positive terminal of the twin hooters. Then, connect the hooters' negative terminals to the vehicle's ground (Earth). Finally, use the existing single hooter's connection to trigger the relay by connecting it to terminal 86, and ground the relay's terminal 85.