How To Test A Pool Pump Motor Capacitor

How To Test A Pool Pump Motor Capacitor

In this video, we take a look at how to test a pool pump motor capacitor with a multi-meter. If your pool pump motor makes a humming sound when you try to turn it on, then following these steps can help you determine if you need a new capacitor or a new motor.

Where Is the Motor’s Capacitor?

  • The backend of the motor, next to terminal connections. Example: UST1102
  • The hump on top of the motor, sometimes called the capacitor dog house. Example: B2854

Not all motors have a serviceable capacitor; many above ground pool pump motors do not have a capacitor under the motor endcap or hump.

Steps to Testing Capacitor

  1. Shut off power to motor at the breaker.
  2. Remove endcap cover and/or in the capacitor dog house.
  3. Unmount the capacitor from the back of the motor.
  4. Use an insulated screwdriver to discharge any residual charge from the capacitor by crossing both terminals with the screwdriver tip.
  5. Take a picture of capacitor wiring to ensure rewiring is done correctly.
  6. Remove wires from the capacitor’s terminal leads using needle-nosed pliers.
  7. Check capacitor for damage or defects, specifically scorch marks, melting, or bulging of the barrel. 
  8. Set Multimeter to Capacitance for a test. Also, check the capacitor barrel for the microfarad rating. 
    1. Run Capacitors list a single microfarad rating; for example, 25 MFD, and 30 MFD. On the other hand, start capacitors list a range of microfarads like 124-149 MFD or 161-193 MFD.
  9. Hold the multimeter’s test leads to capacitor terminals to begin the test. It may take a few seconds for the meter to show a reading. Note the Reading.
  10. Then flip the leads to test the terminals in reverse. Note the Reading.
  11. Compare readings to the capacitor’s ratings. For example, the start capacitor is rated 124-149 MFD; the two test results were 133 and 132.8. Therefore, the capacitor has passed the capacitance test. However, the capacitor failed the test if it was outside of the listed range.
    1. For Start Capacitors, you’ll see a single rating with a plus or minus percentage; Your readings will need to fall within this margin to pass. For example, a run capacitor rated for 30 MFD, ± 6%; your capacitor would need to fall between 28.2 – 31.8 MFD.
  12. If your capacitor fails its capacitance test visit Inyo Pool’s motor parts section to find your replacement Run and Start capacitors

Related Article – How To Find the Right Capacitor For Your Pool Pump Motor

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