How to Read Automobile Wiring Diagrams

by Eli Laurens

Automotive wiring has been standardized over the decades, and most cars will have "color-coded" wiring for lighting, radio, ignition, and secondary systems. This color coding makes it easier for the layman to quickly repair most automobile wiring issues. You can learn to understand the wiring diagrams by following some basic principles.

Understanding colors

Locate the source of the electrical problem, such as a damaged relay. Find the location of the issue shown in the diagram. The repair manual will provide troubleshooting steps to determine which electrical component is damaged or malfunctioning.

After locating the faulty part on the diagram, usually by labels or shape, the colors of wire on the page should exactly match the wire colors in the vehicle. This will assist in tracing the wire back to it's power source, or on to the next electrical circuit. Symbols on the diagram could vary, but typically follow electrician standards.

In rare cases, the diagram could be in black and white, or printed without colors. This is when the "path", or lines on the schematic become important. Sometimes, there may even be very small text next to each line, designating what color it is. This can appear as "DRK GRN" for dark green, or "YEL/BLK" for a yellow wire with a thin black stripe.

Tip

  • check Use a circuit tester to ensure polarity.

Warning

  • close Disconnect the vehicle's battery when any wire repairs are to be made.

Items you will need

About the Author

Eli Laurens is a ninth-grade physics teacher as well as a computer programmer and writer. He studied electrical engineering and architecture at Southern Polytechnic University in Marietta, Ga., and now lives in Colorado.

Photo Credits

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