When locating a wire short as described, what is the initial test setup?

• A. Leave all wires connected and measure resistance across the main panel.
• B. Disconnect all wires from the main panel and measure resistance with a multimeter set to ohms.
• C. Apply high voltage to the circuit and observe spark length.
• D. Only test the output from the main transformer.

Answer: (B)

Starting with the circuit de-energized and isolated gives you a clean, safe baseline to find a short. Disconnecting all wires from the main panel removes energy and any other paths through devices, so the multimeter’s ohms reading reflects only the wiring and connected components you deliberately reintroduce. Measuring resistance with the meter set to ohms lets you see whether there is unexpected continuity (a short) between conductors or to ground. A near-zero resistance where there should be insulation or separation points to a fault, while infinite resistance indicates no unintended path.

If you leave wires connected, the circuit is energized and readings will be unreliable or dangerous to obtain. Using high voltage to observe sparks is unsafe and not how you diagnose shorts. Testing only the transformer output may miss shorts located further along the wiring or in connected devices, so it’s not adequate as an initial setup.