When it comes to 2-wire deep well submersible pumps, the pump starting controls are located inside the pump. Any of these components can fail and cause the pump to become inoperable. By installing a 3-wire pump, those components would be located inside a CONTROL BOX, making repairs much easier when failure of these components are the cause of your pump not operating. Of course if the pump has failed due to burnt motor windings or some other cause, would would still need to pull and replace the pump, but you would have a better understanding of the pump status when the pump starting components are above ground as opposed to 50-500 feet or more, below ground.