Wire Gauge

• Wires come in a variety of sizes called gauges. In automotive wiring, the smaller the gauge number, the thicker the wire. Larger wire is designed to carry more amperage. Power supply wire to an electrical component could be as large as 12 gauges. Wires leading to speakers may be as small as 20 gauges.
  
  

Wire Colors

• The insulation on electrical wire comes in an almost endless variety of colors. The color does not determine how well the wire works, but rather helps to identify the purpose of the wire. In general, for automotive use, black or green wires are grounds; red or other colors of wire are load carrying. Consult a wiring diagram for the vehicle you are repairing so you can follow the color code or make a chart of what colored wires you use for each purpose for future reference.
  
  

Connections

• When adding to or repairing existing electrical systems, each splice or terminal should be made using a solderless or soldered and shrink tube connection system. Twisting wires together or wrapping wires around connection screws will work for a time but are prone to failing.