The good news is that there are some tests that can be performed without having to pull the pump and motor from the well. You will need an ohmmeter and either the online version or hard copy of the Franklin Electric AIM (Application/Installation/Maintenance) Manual for Submersible Motors.

I have outlined some troubleshooting steps below to help investigate problems with your Submersible Pump Motor.

Caution! Electricity can be very dangerous, especially if you are inexperienced. Always use caution working with electricity and turn off power supply breakers when testing components within the electrical system. If you are not 100% confident you can perform any of these tests safely, call a professional.

1. Check Insulation Resistance. Turn off master breaker and disconnect all leads from control box or pressure switch to avoid electric shock hazard and damage to the meter. If you have a QD type control box, remove the lid. Set ohmmeter to R X 100K and zero the meter. Connect one lead to one of the motor leads and one lead to the metal drop pipe or a ground. If the ohms value is normal (see Table 47 of AIM Manual), the motor is not grounded and the cable insulation is not damaged. If the ohms value is below normal, either the windings are grounded or the cable insulation is damaged. Check the cable at the well seal as the insulation is sometimes damaged by being pinched.
2. Check Winding Resistance. Turn off master breaker and disconnect all leads from control box or pressure switch to avoid electric shock hazard and damage to the meter. If you have a QD type control box, remove the lid. Use a multi-meter set to 20 ohms or an ohmmeter set to R X 1 for values under 10 ohms. Use next scale up for values over 10 ohms. Zero the meter. On 3-wire motors measure the resistance of yellow to black (main winding) and yellow to red (start winding). On 2-wire motors: measure the resistance from line-to-line. Three-phase motors: measure the resistance line-to-line for all three combinations. If all ohms values are normal (Tables 13, 22, 24, 25, & 27 in AIM Manual), the motor windings are neither shorted nor open, and the cable colors are correct. If any one value is less than normal, the motor is shorted. If any one ohm value is greater than normal, the winding or the cable is open, or there is a poor cable joint or connection. If some ohms values are greater than normal and some less on single-phase motors, the leads are mixed. See page 48 in AIM Manual to verify cable colors.

If you are getting readings outside of the ranges listed in the AIM Manual you may have a problem with a splice connection down the well or it may, in fact, be the motor. Make sure to perform the same tests again after the motor is pulled from the well. Also, when testing prior to pulling the pump you need to account for the voltage drop that occurs. Please refer to AIM Manual page 47 for the adjustment values.

Hopefully this blog has given you some insight or a solution to your problem. You can also check out our video titled “Troubleshooting 4" Submersible Motor: Insulation & Windings Resistance” on the RC Worst YouTube Channel or give our experts a call at 855.329.4519.