The run winding on a compressor has a resistance of 0 Ω. This indicates that:

• A. The winding is shorted.
• B. The winding is open.
• C. The insulation is intact.
• D. The motor is energized.

Answer: (A)

A low, nearly zero ohm reading across the run winding means a shorted winding. When turns within a coil short to each other (or to the motor housing/ground), the coil presents a direct, very low resistance path instead of its normal finite resistance. That’s why you see 0 Ω. A shorted winding can cause excessive current, overheating, and loss of starting torque or motor failure.

If the winding were open, you’d see infinite resistance, not near zero. If the insulation were intact, the DC resistance would still be a finite value, not zero. And testing resistance while the motor is energized isn’t valid—the measurement should be made with the power removed.