Wires (Opel Vectra B)

For individual colored wires, you usually only see the ends, as they are often laid in bundles in insulated hoses.

When carrying out work independently, it is important that the cross-section of the wire is selected depending on the power of the given consumer (his current needs). The control lamp uses a 0.5 mm² wire, while a 16 mm² wire is used between the battery and the starter. A wire that is too thin heats up and the voltage drops. Then instead of the desired 12 V at the headlights, maybe only 10 or 9.5 volts are supplied - the light becomes dim.

Source is on this resource: www.OPELBOOK.ru