When testing resistance in a motor, what does a high resistance reading usually indicate?

A high resistance reading in a motor typically indicates an open winding. When a winding is open, it means that there is an interruption in the electrical path, preventing current from flowing through that winding. This is characterized by a high resistance value, as there is no complete circuit for the current to travel through.

In practical terms, when you measure resistance across the motor windings and get a high value, this suggests that one or more of the segments of the winding have become disconnected or broken. This condition can lead to the motor failing to operate as expected, because without a complete circuit, the magnetic fields necessary for motor operation cannot be established.

A low resistance reading, conversely, might indicate a shorted winding, where the winding turns are improperly connected, allowing current to bypass parts of the winding. Normal operation would typically show a resistance reading that falls within the motor's designed specifications, far lower than that associated with an open winding. Ground faults would indicate a different issue altogether, generally relating to unwanted electrical paths to the ground, which would usually show as a very low resistance or even a short circuit reading.