What does a motor run winding resistance of 3 ohms indicate if it is expected to read 8 ohms?

A motor run winding resistance reading of 3 ohms, when an expected reading is 8 ohms, indicates an issue with the winding. When there is a reduction in resistance, it often suggests that the winding has experienced damage that causes the turns of the wire within the winding to connect to one another more directly than intended, which is known as winding shorting. This can reduce the total resistance and cause the motor to operate inefficiently or to fail to operate altogether.

Typically, if the winding were open, the resistance would read as infinite (or an extremely high value), while a grounded winding would present a resistance reading of zero or something very low due to a direct connection to the frame or ground. Operating correctly would maintain the expected resistance level. Therefore, the lower resistance measured clearly points to a winding shorting condition.