Submersible Pump Motor Troubleshooting: Winding Resistance and Insulation Resistance

For nearly a century, submersible pumps have been an effective solution for transferring water from well systems to its final destination inside a structure or home. While designed to operate totally submersed in the water which is being pumped, this well water pump stands out in the fact that it can be installed without the worry of freezing.

A submersible pump motor contains leads/wires, which supply power to the motor windings. Submersible pumps either come with two wires (plus one addition wire, which is a grounded lead) or three wires (plus one additional wire, which is a grounded lead). Two-wire motors are 1.5 HP and below and do not require a control box as starting components are internal to the motor. Three-wire motors require an external control box or starter. Two-wire motor leads connect to the pressure switch while three-wire motors leads connect to the control box.

Due to the importance a motor holds on the submersible pump system, if the pump were to malfunction, testing the motor is a good place to start in order to get a diagnosis. Since the pump is located in the well, ensuring the motor is functional is highly recommended prior to the installation. This can be done by measuring and testing the winding resistance and insulation resistance, which determine if the motor is defective. These tests serve as a troubleshooting tactic for both new and used motors.


Highly recommended prior to installation and for maintenance and troubleshooting purposes, a submersible pump motor will need to be tested. A megohmmeter (megger) or ohmmeter connect to the motor leads and can be the best method to determining if the motor windings have an electrical short or are open, thus effecting the performance of the motor itself. The ohmmeter is recommended for winding resistance and the megohmmeter for insulation resistance. Once the appropriate values have been measured, reference the published values for the pump manufacturer’s motor selection. View the videos below to see each test in action.


The submersible motor not only drives the pump but the horsepower of this component, matched with the pump, also determines the pressure and gallons per minute provided by the well system. Based off of its importance to the function of the pump, it is pertinent that the motor is operating efficiently – and winding resistance and insulation resistance testing are two ways in which to test this fact.

To learn more about how to measure and test a submersible pump motor’s winding resistance and insulation resistance, take the ‘Checking Submersible Pump Motor Insulation Resistance with a Megohmmeter’ and ‘Checking Winding Resistance of a Submersible Pump with an Ohmmeter’ AYU courses. For A.Y. McDonald’s proper winding resistance and insulation resistance values, consult our A.Y. McDonald Submersible Motors IOM Manual.