What does a reading of 0 Ω on the run winding indicate?

• A. The winding is shorted.
• B. The winding is open.
• C. The winding is correctly connected.
• D. The winding is not energized.

Answer: (A)

When you test a run winding with an ohmmeter, you’re checking for the coil’s expected finite resistance. A healthy winding has some resistance determined by the length and gauge of the conductor and the temperature. A reading of 0 ohms means there is essentially a direct electrical path with no resistance through the winding, which indicates a shorted condition somewhere in the coil or a short between conductors. In other words, part of the winding has become a bypass path, so current can flow with virtually no opposition.

An open winding would show infinite resistance because there’s no continuity in the coil at all. If the winding were correctly connected and not energized, you would expect the meter to show the normal finite resistance, not zero. The status of being energized or not is separate from the resistance reading obtained with the meter.