Why ground wire burn up its connected to neg battery?

Ground wires do not burn up if they are connected to the negative battery terminal. Ground wires are typically connected to the vehicle's chassis or frame, which provides a low-resistance path for electrical current to flow back to the battery. This prevents electrical components from becoming damaged due to excessive voltage.

If a ground wire appears to have burned up, it is likely due to a short circuit or other electrical fault in the vehicle's wiring system. This can be caused by damaged insulation, loose connections, or faulty electrical components. It is important to have any burned or damaged ground wires inspected and repaired by a qualified mechanic as soon as possible to prevent further damage to the vehicle's electrical system.