What is one method to locate an open circuit using a wiring diagram?

• A. Trace from the load toward the source on the diagram and perform continuity checks.
• B. Trace from the power source toward the load on the diagram and perform continuity checks.
• C. Inspect only the connectors visually.
• D. Power the circuit and monitor for voltage drop across the entire harness.

Answer: (B)

When using a wiring diagram to locate an open circuit, you follow the path from the power source toward the load and test continuity along each segment as you go. This approach uses the diagram’s sequence to pinpoint exactly where the current path is broken. By starting at the source, you quickly identify the first section that fails continuity, which isolates the open to a specific wire, connector, or splice. Testing in order also helps confirm that the portions beyond the break are still intact, making localization efficient and clear.

Visual inspection of connectors alone can miss internal breaks or damaged conductors, so it isn’t reliable by itself. Monitoring voltage across the entire harness while the circuit is powered isn’t precise for locating an open; with an open circuit there may be little or no current and no meaningful voltage drop to indicate the fault. Using a continuity check as you trace from source to load provides a direct, practical way to find the fault location on a wiring diagram.